Retinaldehyde (Retinal)

Five are trial figures that link to the paper, one is the source of a marketing claim, two are computed from the label decode lower on the page.

1. 0.05% and 0.05%

   Retinaldehyde 0.05% and tretinoin 0.05% both cut wrinkle and roughness measurements significantly by week 18 in the one trial that ran them side by side (125 patients, double-blind, 44 weeks), and the vehicle did not. Retinaldehyde "was well tolerated during the entire study"; tretinoin "caused more local irritation, and affected compliance of the patients". ²

   Creidi 1998. The abstract reports the direction and the significance of each arm against vehicle, not the size of the change and not a test of one arm against the other, and says the effect in both active arms was less pronounced at week 44 than at week 18. Two of its authors were Pierre Fabre researchers (the maker of Avène's retinaldehyde line); funding is not stated.

2. 30% vs 28%

   Tretinoin 0.1% and 0.025% produced the same epidermal thickening over 48 weeks (30% vs 28%, against an 11% loss on vehicle) and the same increase in dermal blood vessels (100% vs 89%). The 0.1% arm had significantly more erythema and scaling. Four times the dose, the same result, more irritation. ⁹

   Griffiths 1995, 99 patients, double-blind, three arms. On retinol, 0.3% and 0.15% did not differ at 8 weeks in a 40-person pilot, and neither did their side effects (Zasada 2020). On retinal, see the next number.

3. 12 weeks: no · 24 weeks: yes

   Retinaldehyde 0.1% and 0.05% reached the same overall improvement at 12 weeks (95% of 40 women), the same texture change (13.7% vs 12.6%) and the same water-loss change, with no difference in tolerability; only the melanin index separated them, improving 6.5% on 0.1% and not significantly on 0.05%. A 2026 split-face comparison of the same two strengths over 24 weeks in 56 women found both worked and the wrinkle reductions were larger on the 0.1% side. ²⁸

   Kwon 2018; Deda 2026. Read together: 0.05% is the strength to start on and the one with the head-to-head against tretinoin; 0.1% has a case for pigment at three months and for wrinkles at six. Above 0.1% there is no trial.

4. 0.01%, 0.025%, 0.6%

   The concentration each form needed to switch on the skin's retinoic-acid-metabolising enzyme under occlusion: 0.01% retinaldehyde, 0.025% retinol, 0.6% retinyl palmitate, against 0.001–0.05% for retinoic acid itself. That is the ladder as a measurement: retinal needs about 2.5 times less than retinol, and retinyl palmitate about 24 times more. ¹

   Duell 1997, human skin in vivo, 4-hydroxylase induction as the potency proxy. The dose response for retinol stopped being linear above 0.25%, and for retinaldehyde above 0.5%.

5. 11.5×, in a test tube

   The "retinal is 11 times faster than retinol" line on the Medik8 page and its imitators traces to one measurement: cultured keratinocyte cytosol made retinoic acid from retinal at 51.6 pmol per hour per mg of protein and from retinol at 4.49. It is an enzyme-kinetics result from 1990, not a clinical one, and no trial on this page reproduces an 11-fold difference in what skin does. ²³

   Siegenthaler 1990. The one head-to-head at matched strengths (Kim 2021: 0.05% and 0.1% encapsulated retinal against 0.05% and 0.1% plain retinol, 23 volunteers, 8 weeks; a different Kim 2021 paper, also with 23 participants, is the acne pilot cited lower down) found retinal ahead on every measure but dermal density, with no multiple stated.

6. 49% vs 37%

   For acne, adapalene 0.1% gel reduced total lesions 49% at 12 weeks against 37% for tretinoin 0.025% gel (323 patients), with less retinoid dermatitis. Across five trials and 900 patients the meta-analysis called them equivalent on efficacy, adapalene faster to act and with "considerably greater local tolerability". ³³

   Shalita 1996; Cunliffe 1998. Adapalene 0.1% has been over the counter in the US since 2016; it is the one prescription-class retinoid in the picks.

7. 7 of 22

   7 of the 22 retail retinoids we decoded state no percentage anywhere: CeraVe, La Roche-Posay, RoC, Olay, Neutrogena, BIYSBER, Amazon Basics. In CeraVe's serum the encapsulated retinol is 19th of 33 ingredients; in Neutrogena's, 23rd of 29. Ingredients above 1% are listed in descending order, so those positions put the retinol below 1% and, given what sits above it, likely far below. ⁴⁹

   Label decode below, read from brand and retailer pages: 10 state the percentage in the product name, 3 on the brand page, 2 on a Drug Facts label. Biysber publishes no ingredient list at all.

8. 9 of 22

   9 of the 22 are encapsulated, in the brand's own words: CeraVe, RoC, Medik8 ×2, Naturium ×2, Prequel, Paula's Choice, PURITO (Biysber, with no readable list, is the one unknown). Encapsulation changes how much of the stated percentage reaches the skin and when, so an encapsulated 0.05% retinal and a plain 0.2% retinal are not four times apart in what the skin sees at once. The only trial here of an encapsulated retinal against a plain retinoid ran it against retinol rather than plain retinal. ³

   Label decode below; "encapsulated" is the brand's word, quoted in the table. Kim 2021 for the trial.

Each form has to be converted to retinoic acid before the skin can use it, and each conversion step costs potency. The rungs below are ordered by that, with the strength at which each has a result, because that is the strength to buy. The picks count the rungs from retinol: esters are below the first rung, HPR is beside the ladder.

Retinoids do the same things at every rung, faster and with more irritation as you climb. The question is which job you are buying it for, because the trials were run one job at a time.

• Works Acne, blackheads and clogged pores — Adapalene 0.1%: −49% total lesions at 12 weeks against −37% on tretinoin 0.025%, and the 2024 acne guideline puts topical retinoids at the core of treatment. Retinaldehyde 0.05% is the one cosmetic retinoid with measured antibacterial action (C. acnes down 100-fold in two weeks), which makes it the cosmetic fallback. ³³
• Works Fine lines and photodamage — The 44-week retinal-and-tretinoin trial above; retinol 0.1% improved crow's feet 44% over a year on the face, and 0.4% moved fine wrinkling on naturally aged arm skin in 24 weeks. Expect the measurable change at 12 to 24 weeks. ²⁵
• Helps, not alone Dark spots and uneven tone — The endpoint that responded to strength at 12 weeks: retinaldehyde 0.1% improved the melanin index 6.5% where 0.05% did not significantly, and 0.1% retinol improved mottled pigmentation 84% over 52 weeks. Slow: plan on a year. ²⁸
• Helps, not alone Oiliness — A 0.05% retinaldehyde niosome cut sebum from 328 to 251 µg/cm² in four weeks in a 23-person pilot with no control arm. Direction is right; the trial is small and open. ²⁰
• Wrong tool Deep wrinkles, sagging — No rung reverses structural loss. Tretinoin thickens the epidermis and increases dermal blood supply; the trials measure fine wrinkling, roughness and tone, and say so. ⁹

Skin does not use retinol; it uses retinoic acid. Retinyl esters are hydrolysed to retinol, retinol is oxidised to retinal, retinal is oxidised to retinoic acid, and retinoic acid binds the nuclear receptors that change how keratinocytes grow and how much collagen fibroblasts make. Every rung is a count of how many of those steps the skin still has to do.

• Study Retinol at up to 1.6%, applied under occlusion for four days, thickened the epidermis 1.5-fold, the same as 0.025% retinoic acid (1.6-fold), while producing no measurable retinoic acid in the skin and no erythema, where retinoic acid raised the erythema score 3.7-fold. The skin converts what it needs and stores the rest as retinyl esters, which rose 240-fold. ²²
• Study In cultured keratinocytes retinoic acid was formed from retinal at 51.6 and from retinol at 4.49 pmol per hour per mg protein. This is the whole basis of the "11 times" claim. ²³
• Study Retinaldehyde also acts on bacteria directly, which retinol and retinoic acid do not: significant activity against S. aureus and C. acnes in vitro, and a 100-fold fall in C. acnes counts after two weeks of 0.05% on 22 foreheads. ¹⁴
• Review "Retinol and retinyl esters are not irritant, whereas demonstrating only a modest clinical efficiency. On the other hand, retinaldehyde, which is fairly well tolerated, seems to be the most efficient cosmeceutical retinoid." ³⁶

The trials applied once daily (most) or twice (Kwon) for 12 to 52 weeks and measured at 4, 8, 12, 24 and 44–52 weeks. Use the schedule as the trials did, and judge at the week the trial judged.

1. Weeks 0–4 Three nights a week, a pea for the face, on dry skin, moisturiser after. Retinol 0.2–0.5% or retinal 0.05%. Dryness and flaking in these weeks is retinoid dermatitis, a dose-dependent receptor effect rather than an allergy; it fades as the skin adapts. If it does not, drop to two nights and keep the strength.
2. Weeks 4–8 Nightly. Sunscreen every morning, which the trials required. Tucker-Samaras 2009 saw significant change in some measures at week 4 on 0.1% retinol; the encapsulated retinal trial measured at 8. Nothing on this page reports a result before week 4.
3. Week 12 Judge texture, lines and (for adapalene) acne. The 12-week endpoint of Kwon 2018, Babcock 2015, Draelos 2020 and Shalita 1996. If nothing has changed on a stated-percentage product, climb a rung; if nothing has changed on an undisclosed one, buy a stated one.
4. Weeks 24–52 Judge pigment and photodamage. Kafi measured at 24 weeks, Creidi at 18 and 44, Randhawa at 52. Creidi's abstract says the week-44 effect was less pronounced than week 18 on both retinal and tretinoin: expect a plateau.
5. Any week Do not double the dose to speed it up. Tested on every rung (Griffiths, Kwon, Zasada): the same result on lines and texture within the trial, and more irritation on tretinoin. The 24-week retinal comparison is the one case for a higher strength, and it is a case for six months at 0.1%.

A retinoid is the one active in a routine that sets the schedule for everything else. Most pairings are about tolerance; one is about chemistry.

Pregnancy is not a pairing question but it belongs here: the labels say the data are insufficient, the registry study found no signal, and the standing advice is still to stop. See the routing table.

In the order the trials measured it: dryness first, texture by 8–12 weeks, lines by 12–24, pigment by 24–52. The number on the bottle does not move these dates; the rung does, a little.

1. Weeks 1–3 Dryness, flaking, some redness. Retinoid dermatitis, dose-dependent. Tretinoin 0.1% produced significantly more of it than 0.025% over 48 weeks for the same result. ⁹
2. Week 4 First measurable change on retinol. Significant differences from vehicle on several photodamage measures at week 4 on 0.1% stabilized retinol, progressing to week 8. ³²
3. Week 8 Texture and wrinkle depth on retinal. Encapsulated retinaldehyde at 0.05% and 0.1% significantly improved wrinkle depth and biophysical measures at 8 weeks, ahead of plain retinol at the same two percentages on every measure but dermal density. ³
4. Week 12 The acne endpoint; the retinal endpoint. Adapalene 0.1%: −49% total lesions (Shalita 1996). Retinal 0.05% and 0.1%: 95% improved overall, texture +12.6% and +13.7% (Kwon 2018). ³³
5. Week 24 Fine wrinkling on retinol; overall improvement on tretinoin. Retinol 0.4%: fine-wrinkling score −1.64 vs −0.08 on vehicle, on naturally aged arm skin (Kafi 2007). Tretinoin 0.05%: 79% of subjects improved vs 48% on vehicle (Weinstein 1991). ²⁶
6. Weeks 44–52 Pigment; and the plateau. 0.1% retinol: crow's feet improved 44%, mottled pigmentation 84% at 52 weeks (Randhawa 2015). Retinal and tretinoin at 44 weeks: still ahead of vehicle, less pronounced than at 18 (Creidi 1998). ²⁵

Every pick is a strength with a trial behind it, or the on-ramp to one, at the lowest Amazon price we found with a stated percentage. Nothing here states no percentage; the products that do are in the cut list with the reason. Prices are Amazon's on the day this page was built; strengths are as the product states them.

1. 

   Rung one: retinol at a trial strength

   The Ordinary Retinol 0.5% in Squalane

   0.5% · oil serum · 30 mL · $9.30

   The closest shelf strength to the 0.4% that moved fine wrinkling on naturally aged arm skin over 24 weeks (Kafi 2007) and to the 0.5% arm that matched 0.05% tretinoin side by side (Babcock 2015). $9.30, plain retinol, percentage in the name, retinol fourth of eight ingredients.

   Plain retinol in oil oxidises; keep it out of light and use it within months. If you have never used a retinoid, start on the 0.2% below for a month.

   Check price on Amazon

2. 

   Rung one, the on-ramp

   The Ordinary Retinol 0.2% in Squalane

   0.2% · oil serum · 30 mL · $8.10

   No trial on this page tested 0.2%; it is here as the tolerance step both dermatologists in the panel recommend before a trial strength, and it is the cheapest stated-percentage bottle in the decode. Three nights a week for a month, then move to the 0.5%.

   A tolerance bottle. If it does nothing, that is expected; the 0.5% is where the evidence starts.

   Check price on Amazon

3. 

   Rung two: the trial-strength retinal

   Naturium Retinaldehyde Cream Serum 0.05%

   0.05% · cream serum · 50 mL · $20.00

   The strength Creidi 1998 ran against 0.05% tretinoin in 125 patients for 44 weeks (a plain cream), the strength Kwon 2018 found did everything 0.1% did at 12 weeks except the melanin index, and, encapsulated, the strength Kim 2021 trialled against retinol for 8 weeks. Fragrance-free, sold by Amazon.

   Retinaldehyde sits 20th of 37 in the ingredient list; the 0.05% is the brand's figure. Encapsulation means it is not comparable gram for gram with The Ordinary's plain 0.2% emulsion.

   Check price on Amazon

4. 

   Rung two, for pigment or the long run: retinal 0.1%

   Naturium Retinaldehyde Cream Serum 0.10%

   0.1% · cream serum · 50 mL · $25.59

   The strength that improved the melanin index at 12 weeks where 0.05% did not (Kwon 2018) and that led on wrinkles at 24 weeks (Deda 2026). Same encapsulated base as the 0.05% above, $5.59 more, sold by Amazon.

   Start on the 0.05% unless you have used a retinoid before; the 24-week result is a case for staying on 0.1%, not for starting there. Above 0.1% there is no trial, which is why The Ordinary's 0.2% emulsion is in the cut list.

   Check price on Amazon

5. 

   Rung one, the top: retinol 1%

   The Ordinary Retinol 1% in Squalane

   1% · oil serum · 30 mL · $11.90

   The 1% arm matched tretinoin 0.1% side by side over 12 weeks (Babcock 2015), and it is $11.90, plain, percentage in the name. For someone who has tolerated 0.5% for months and wants the top of the rung before moving to retinal or a prescription.

   Not a starting point: The Ordinary itself files 1% under advanced users.

   Check price on Amazon

6. 

   Rung three, over the counter: adapalene for acne

   Glenmark Therapeutics Adapalene Gel 0.1%

   0.1% · gel · 15 g · $8.49

   The one prescription-class retinoid sold without one. Adapalene 0.1% beat tretinoin 0.025% on total lesions (49% vs 37% at 12 weeks, 323 patients) and was better tolerated across 900 patients in five trials. This generic lists the same active and near-identical inactives as Differin at 35% less per gram.

   Listed on Amazon by Glenmark, a third-party seller; check the seller before paying. For acne. The photoaging trials on this page were run on tretinoin, retinal and retinol.

   Check price on Amazon

Cut: CeraVe Resurfacing Retinol (the retinol serum the community names most after The Ordinary's, in 39 of the 1,677 field-report comments; no stated percentage, retinol 19th of 33, alcohol in the list; fine for a first month, which is what the comments use it for); The Ordinary Retinal 0.2% Emulsion (the cheapest retinal per gram, at twice the highest strength any trial tested); Medik8 Crystal Retinal 3 and 6 (encapsulated 0.03% and 0.06%, 30 mL, $66 and $87: nine and six times the Naturium's price per gram of retinal, for stated doses that bracket the Naturium 0.05%); Prequel Retinal Renew 0.1% ($28.99, sold on Amazon by the brand's own store; the Naturium 0.10% is the same stated strength for $3.40 less, from Amazon itself); Paula's Choice Pro Retinaldehyde ($68, sold by the brand rather than through Amazon); PURITO retinol 0.1% + retinal 0.1% (two rungs in one bottle); Differin brand ($12.97 for 15 g against the Glenmark's $8.49 for the same label); the two Granactive 2% products (no trial, HPR share undisclosed); every other serum that states no percentage. Picks are limited to products listed on Amazon. Amazon prices on the day this page was built; they change. Affiliate links; we earn a commission at no cost to you.

The line sells most of the retinal on the shelf. It has a document behind it; here is what the document measured.

Retinoic acid formed from retinal, keratinocyte cytosol

51.6pmol per hour per mg protein (Siegenthaler 1990) ²³

Retinoic acid formed from retinol, same assay

4.49the ratio is 11.5, measured in cultured cells ²³

Concentration for enzyme induction in living skin

0.01% vs 0.025%retinal vs retinol under occlusion, about 2.5 times (Duell 1997) ¹

Clinical trials reproducing an 11-fold difference

0the one matched head-to-head (Kim 2021, encapsulated retinal vs plain retinol at 0.05% and 0.1%) found retinal ahead on every measure but dermal density; no multiple stated ³

• Brand "Retinal is 11 times faster acting than traditional retinol." — Medik8, Retinal Guide. ⁴⁴
• Editorial Get The Gloss repeats the figure and flags it in the same sentence as "conducted in a petri dish rather than living skin". ⁴⁶
• Chemists Chemist Confessions, reading a matched-strength study they do not name: 0.05% retinal performed on par with 0.05% retinol, "a far cry from the claim that retinal is 10x more effective than retinol". The one matched trial we could identify (Kim 2021, encapsulated retinal) found retinal ahead; whether they read that paper or another, the two readings disagree only on the size of a gap both put far below eleven. ⁴¹

The number on the front carries the pitch, so we checked which form of vitamin A is actually in the bottle, whether a percentage is stated anywhere, where the retinoid falls in the ingredient list when it is not, whether it is encapsulated, and what a gram of the active costs.

Fragrance

10%2 of 21 products

Denatured alcohol

10%2 of 21 products

Encapsulated

43%9 of 21 products

• 15 of 22 state a percentage: 10 in the product's name, 3 on the brand page, 2 on a Drug Facts label (the adapalene gels, which are OTC drugs and must). 7 state none: CeraVe, La Roche-Posay, RoC, Olay, Neutrogena, BIYSBER, Amazon Basics.
• Where no percentage is stated, position tells you the ceiling: CeraVe's encapsulated retinol is 19th of 33, Neutrogena's 23rd of 29, Amazon Basics' 15th of 32, Olay's 6th of 23 and La Roche-Posay's 11th of 22. Ingredients above 1% are listed in descending order; below 1% the order is free. Two of these (La Roche-Posay, Olay) blend retinol with an ester, which is a second undisclosed amount.
• 9 of 22 are encapsulated, in the brand's own words (quoted in the table): 7 of the 8 retinal products, and two retinols (CeraVe, RoC); Biysber, with no readable list, is unknown, so the tile above counts 9 of 21. An encapsulated 0.05% and a plain 0.2% are not four times apart in what the skin sees at once.
• Two products sold as "Granactive Retinoid 2%" are 2% of a supplier complex; neither brand states the share that is hydroxypinacolone retinoate. We list them at 2% because that is the label, and price them per gram of complex, which flatters them.
• Per gram of stated active, inside one rung: retinol runs $40 (The Ordinary 1%) to $135 (The Ordinary 0.2%); retinal runs $422 (The Ordinary 0.2%) to $7,333 (Medik8 Crystal Retinal 3, 0.03%, $66). The 17-fold spread in retinal is the cost of encapsulation, packaging and brand, and the Naturium 0.05% sits at $800.
• 2 of the 21 with a readable list carry fragrance (La Roche-Posay, Neutrogena). None of the retinals do.
• The two adapalene gels list identical actives and near-identical inactives on DailyMed; Glenmark's generic is $566 per gram of adapalene against Differin's $865 in the 15 g size.

Percentages are as the product states them; "% stated where" says where, and a ? marks a percentage not on the label. Encapsulated is the brand's word. Position = where the retinoid falls in the ingredient list, 1-based. $/g active = price ÷ (size in mL × stated %), treating the product as water; blank where no percentage is stated, comparable only within one form, and for PURITO computed on its retinal alone. Prices in this table are the retailer's list price at the URL read; the picks above use Amazon's price on the build date.

Two guidelines (the AAD's public retinoid page and its 2024 acne guideline), three reviews, four of the trials themselves, two dermatologists, two cosmetic chemists, a pharmacist, three brand pages and three editorial guides. Not in the table because they could not be fetched: Paula's Choice's script-rendered ingredient dictionary and strength guide (its product page was readable, and that product is in the decode), Byrdie and Allure (blocked), ACOG's pregnancy page (paywalled), Dr Dray (video only), Wirecutter and Skincarisma (no page on retinal).

Harvested from r/SkincareAddiction, the largest community where people ask which retinoid to start and what went wrong, then filtered to the comments that themselves name a retinoid (retinol, retinal, tretinoin, adapalene, granactive) or a retinoid product. The shares below are of those comments, not of the whole harvest. Every quote is verbatim and links to the comment. The brand list at the end counts any mention of the brand; CeraVe's 99 includes its cleansers and moisturisers, and 39 of them name its retinol serum.

Reddit search across 7 communities for 15 queries, then each thread's top comments read, up to the harvest's thread cap; the threads that made the cut came from r/SkincareAddiction. 367 threads and 5,039 comments were harvested, of which 1,677 retinoid-naming comments are the denominator here. Themes are keyword matches over that set, each one's quote being a high-scoring comment that carries both the retinoid term and the theme term, verbatim and linked. Harvested 2026-09-19.

• Olivier Sorg, Jean-Hilaire Saurat and colleagues Clinique de Dermatologie, Geneva University Hospital; authors of the 2006 cosmeceutical retinoids review (Saurat is also on the Siegenthaler and Pechere papers)
  Retinol and retinyl esters are not irritant, whereas demonstrating only a modest clinical efficiency. On the other hand, retinaldehyde, which is fairly well tolerated, seems to be the most efficient cosmeceutical retinoid. Dermatologic Therapy, 2006 (abstract) · 2006 ↗
• Victoria Fu and Gloria Lu Cosmetic chemists, Chemist Confessions
  Retinal is one step closer than retinol to converting to the retinoic acid form that your skin's retinoic acid receptors can interact with to kick off all those anti-aging processes. Chemist Confessions, "Retinal - Is it Better Than Retinol?" · 2024-02-08 ↗
• Dr Sam Bunting Dermatologist, Harley Street, London; sells an HPR serum
  What matters is receptor activation, and for that, a molecule that arrives ready to bind will always have an advantage over one that needs your skin's enzymes to finish the job. drsambunting.com, "Which is the right retinoid for me?" · 2026-06-24 ↗
• Dr Shereene Idriss Dermatologist, Idriss Dermatology, New York
  Rather opt for retinol that your skin can tolerate on a long-term basis. dridriss.com, "Retinol for newbies" · 2022-03-29 ↗
• Martina Trabacchi Pharmacist; ISDIN medical communication specialist (a retinal brand)
  While retinol takes two steps to convert, retinal only takes one -- meaning it converts into active form more quickly. isdin.com, "Retinal (with an A): the complete guide" · 2026-03-12 ↗
• Michelle Wong PhD (chemistry), Lab Muffin Beauty Science
  Retinoids are ingredients that work like vitamin A. They have lots of applications in skincare -- their main uses are to help with acne and skin aging (specifically wrinkle reduction and evening out pigmentation). labmuffin.com, "7 common retinoid skincare myths, busted" · 2020-05-07 ↗
• Deanna Pai Contributing writer, NBC Select
  Retinal is considered the most effective retinoid in over-the-counter skin care products. NBC Select, "The best retinal products" · 2026-05-20 ↗

Cited without a named author: the American Academy of Dermatology (two pages), Medik8, The Ordinary, Naturium, INCIDecoder, the FDA labels on DailyMed, MotherToBaby. This page is not medically reviewed; the credentials above belong to the people quoted.

Is retinal better than retinol?

It is one conversion step closer to retinoic acid, and in living skin it needed about 2.5 times less than retinol to switch on the same enzyme (0.01% against 0.025% under occlusion). In the one matched head-to-head, encapsulated retinal beat plain retinol on every measure but dermal density over 8 weeks. It is not eleven times better: that figure is an enzyme rate in cultured cells from 1990. If retinol at a stated 0.5 to 1% has done nothing in 12 weeks, retinal 0.05% is the next rung. ¹³²³

What percentage of retinal should I use?

0.05% to start. That is the strength that ran alongside 0.05% tretinoin over 44 weeks in 125 patients, and the strength that did everything 0.1% did in the 40-woman, 12-week comparison except improve the melanin index. Use 0.1% if dark spots are the goal, or if you are going to stay on it for six months: the 24-week comparison found 0.1% ahead on wrinkles. Above 0.1% there is no trial. ²²⁸¹⁸

Is retinal as good as tretinoin?

At 0.05% each, in the one trial that ran them side by side, both cut wrinkle and roughness measures significantly by week 18 and the vehicle did not; retinaldehyde was tolerated throughout and tretinoin caused enough irritation to affect compliance. The abstract reports each arm against vehicle rather than one against the other, and gives no sizes, so "as good" is a reading of the trial rather than a number from it. ²

Does a higher percentage of retinol work better?

In the trials that tested it, rarely. Retinol 0.3% did no more than 0.15% at 8 weeks; tretinoin 0.1% did no more than 0.025% at 48 weeks and irritated more; retinal 0.1% did no more than 0.05% at 12 weeks except on pigment, and was ahead on wrinkles at 24 weeks. There is a floor: tretinoin at 0.01% and 0.001% did no better than vehicle. Buy the strength with the trial; if you want more, the evidence favours changing rung over changing percentage, with retinal 0.1% as the one exception. ^292892718

Why does my retinol serum not say a percentage?

Because it does not have to; retinol is a cosmetic ingredient. 7 of the 22 products we decoded state none. When the retinol is 19th of 33 ingredients (CeraVe) or 23rd of 29 (Neutrogena) it is below 1% and, given what sits above it, likely far below. Those serums are a low dose by construction, which suits a first month and explains the months after it. ⁴⁹

What does "encapsulated" mean on the label?

The retinoid is held in a carrier (lipid vesicles, calcium particles, a capsule) that releases it over time and protects it from light and oxygen. 9 of the 22 products are. It makes the stated percentage non-comparable with a plain formula, and it is the only form of retinal that has been trialled against retinol at matched strengths. ³⁴⁹

How long until a retinoid works?

First measurable change at 4 weeks on retinol in one trial, wrinkle depth at 8 on retinal, the acne endpoint at 12, fine wrinkling at 24, pigment at 52. Creidi measured retinal and tretinoin at 18 and 44 weeks and found the later effect less pronounced, so expect a plateau. Nothing on this page reports a result before week 4. ^3224252

Which retinoid is best for acne?

Adapalene 0.1%, over the counter: 49% fewer lesions at 12 weeks against 37% on tretinoin 0.025%, better tolerated across 900 patients in five trials, and it kept 75% of responders clear over 16 weeks of maintenance against 54% on vehicle. Retinaldehyde is the cosmetic fallback because it is the only one of the three cosmetic forms with measured antibacterial action. ^33343514

Can I use a retinoid while pregnant?

The tretinoin and adapalene labels say the data are insufficient to establish a risk either way; MotherToBaby says the standing recommendation is to avoid topical retinoids; a Nordic registry of 3.9 million births found 3.3% major malformations after first-trimester topical retinoid exposure against 3.0% without, not a significant difference. The advice to stop stands because the cost of stopping is nothing. Ask whoever is managing the pregnancy. ⁵⁰⁵²¹²

Retinal, retinaldehyde, retinol, retinoid: what is the difference?

Retinoid is the family. Retinol is vitamin A alcohol; retinal (retinaldehyde) is the aldehyde it is oxidised to; retinoic acid (tretinoin) is the acid retinal is oxidised to, and the form the skin's receptors use. Adapalene and HPR are synthetic molecules built to hit the same receptors. Each step up the ladder is one fewer conversion the skin has to do. ³⁸²²

1. 1

   Unoccluded retinol penetrates human skin in vivo more effectively than unoccluded retinyl palmitate or retinoic acid.

   Duell EA, Kang S, Voorhees JJ · J Invest Dermatol 109(3):301-5 · 1997

2. 2

   Profilometric evaluation of photodamage after topical retinaldehyde and retinoic acid treatment.

   Creidi P, Vienne MP, Ochonisky S, Lauze C, Turlier V, Lagarde JM, Dupuy P · J Am Acad Dermatol 39(6):960-5 · 1998

3. 3

   The efficacy and safety of multilamellar vesicle containing retinaldehyde: A double-blinded, randomized, split-face controlled study.

   Kim J, Kim J, Jongudomsombat T, Kim E, Suk J, Lee D, Lee JH · J Cosmet Dermatol 20(9):2874-2879 · 2021

4. 4

   In vitro metabolism by human skin and fibroblasts of retinol, retinal and retinoic acid.

   Bailly J, Crettaz M, Schifflers MH, Marty JP · Exp Dermatol 7(1):27-34 · 1998

5. 5

   Bioconversion of retinol and its cell barrier function in human immortalized keratinocytes cells and artificial epidermis-dermis skin.

   Kim JE, Kim WH, Kim S, Na Y, Choi J, Hong YD, Park WS, Shim SM · Exp Dermatol 32(6):822-830 · 2023

6. 6

   Molecular mechanisms of retinoid actions in skin.

   Fisher GJ, Voorhees JJ · FASEB J 10(9):1002-13 · 1996

7. 7

   Molecular basis of sun-induced premature skin ageing and retinoid antagonism.

   Fisher GJ, Datta SC, Talwar HS, Wang ZQ, Varani J, Kang S, Voorhees JJ · Nature 379(6563):335-9 · 1996

8. 8

   Nuclear hormone receptors inhibit matrix metalloproteinase (MMP) gene expression through diverse mechanisms.

   Schroen DJ, Brinckerhoff CE · Gene Expr 6(4):197-207 · 1996

9. 9

   Two concentrations of topical tretinoin (retinoic acid) cause similar improvement of photoaging but different degrees of irritation. A double-blind, vehicle-controlled comparison of 0.1% and 0.025% tretinoin creams.

   Griffiths CE, Kang S, Ellis CN, Kim KJ, Finkel LJ, Ortiz-Ferrer LC, White GM, Hamilton TA, Voorhees JJ · Arch Dermatol 131(9):1037-44 · 1995

10. 10

    Teratogenicity of high vitamin A intake.

    Rothman KJ, Moore LL, Singer MR, Nguyen US, Mannino S, Milunsky A · N Engl J Med 333(21):1369-73 · 1995

11. 11

    Pregnancy outcome following exposure to topical retinoids: a multicenter prospective study.

    Panchaud A, Csajka C, Merlob P, Schaefer C, Berlin M, De Santis M, et al. · J Clin Pharmacol 52(12):1844-51 · 2012

12. 12

    Topical retinoid use in women of reproductive age and risk of major congenital malformations in exposed pregnancies: a Nordic cohort study.

    Refsum E, Furu K, Cesta CE, Nørgaard M, Wittström F, Zoega H, Ulrichsen SP, Cohen JM · Br J Dermatol 194(4):640-647 · 2026

13. 13

    Retinol and Retinyl Palmitate.

    Johnson W Jr · Int J Toxicol 36(5_suppl2):53S-58S · 2017

14. 14

    The antibacterial activity of topical retinoids: the case of retinaldehyde.

    Pechère M, Germanier L, Siegenthaler G, Pechère JC, Saurat JH · Dermatology 205(2):153-8 · 2002

15. 15

    Clinical efficacy and safety of a topical combination of retinaldehyde 0.1% with erythromycin 4% in acne vulgaris.

    Morel P, Vienne MP, Beylot C, Bonérandi JJ, Dréno B, Lehucher-Ceyrac D, Slimani S, Dupuy P · Clin Exp Dermatol 24(5):354-7 · 1999

16. 16

    Antiaging efficacy of a retinaldehyde-based cream compared with glycolic acid peel sessions: A randomized controlled study.

    Rouvrais C, Baspeyras M, Mengeaud V, Rossi AB · J Cosmet Dermatol 17(6):1136-1143 · 2018

17. 17

    The Clinical Efficacy and Tolerability of a Novel Retinaldehyde Serum with Firming Peptides to Improve Skin Texture and Signs of Photoaging.

    Konisky H, Bowe WP, Yang P, Kobets K · J Drugs Dermatol 23(11):992-997 · 2024

18. 18

    Comparative Evaluation of Topical Stabilized Retinaldehyde 0.1% vs. 0.05% on Skin Biophysical and Biomechanical Parameters.

    Deda A, Odrzywółek W, Lebiedowska A, Banyś A, Bożek M, Kuca D, Wiśniewska N, Wcisło-Dziadecka D, Wilczyński S · Skin Res Technol 32(2):e70326 · 2026

19. 19

    Enhancing Facial Rejuvenation Outcomes With a Novel Retinaldehyde-Based Cream: A Comparative Randomized Intra-Individual Study.

    Monteil C, Barreto-Campos V, Lain E, Guillou E, Doat G, Nocera T · J Cosmet Dermatol 24(12):e70555 · 2025

20. 20

    A pilot study evaluating the efficacy and safety of retinaldehyde-loaded niosomes against mild-to-moderate acne.

    Kim J, Kim J, Lee YI, Suk J, Lee D, Lee JH · J Cosmet Dermatol 20(11):3586-3592 · 2021

21. 21

    Natural Retinol Analogs Potentiate the Effects of Retinal on Aged and Photodamaged Skin: Results from In Vitro to Clinical Studies.

    Brown A, Furmanczyk M, Ramos D, Ribes A, Pons L, Bustos J, de Henestrosa ARF, Granger C, Jourdan E · Dermatol Ther (Heidelb) 13(10):2299-2317 · 2023

22. 22

    Application of retinol to human skin in vivo induces epidermal hyperplasia and cellular retinoid binding proteins characteristic of retinoic acid but without measurable retinoic acid levels or irritation

    Kang S, Duell EA, Fisher GJ, et al. · J Invest Dermatol 1995;105(4):549-56 · 1995

23. 23

    Retinol and retinal metabolism. Relationship to the state of differentiation of cultured human keratinocytes

    Siegenthaler G, Saurat JH, Ponec M · Biochem J 1990;268(2):371-8 · 1990

24. 24

    Improvement of naturally aged skin with vitamin A (retinol)

    Kafi R, Kwak HS, Schumacher WE, et al. · Arch Dermatol 2007;143(5):606-12 · 2007

25. 25

    One-year topical stabilized retinol treatment improves photodamaged skin in a double-blind, vehicle-controlled trial

    Randhawa M, Rossetti D, Leyden JJ, et al. · J Drugs Dermatol 2015;14(3):271-80 · 2015

26. 26

    Topical tretinoin for treatment of photodamaged skin. A multicenter, double-blind, vehicle-controlled study

    Weinstein GD, Nigra TP, Pochi PE, et al. · Arch Dermatol 1991;127(5):659-65 · 1991

27. 27

    Tretinoin emollient cream: a new therapy for photodamaged skin

    Olsen EA, Katz HI, Levine N, et al. · J Am Acad Dermatol 1992;26(2 Pt 1):215-24 · 1992

28. 28

    Efficacy and safety of retinaldehyde 0.1% and 0.05% creams used to treat photoaged skin: a randomized double-blinded controlled trial

    Kwon HS, Lee JH, Kim GM, Bae JM · J Cosmet Dermatol 2018;17(3):471-6 · 2018

29. 29

    Randomized parallel control trial checking the efficacy and impact of two concentrations of retinol in the original formula on the aging skin condition: pilot study

    Zasada M, Budzisz E · J Cosmet Dermatol 2020;19(2):437-43 · 2020

30. 30

    A randomized, double-blind, split-face study comparing the efficacy and tolerability of three retinol-based products vs. three tretinoin-based products in subjects with moderate to severe facial photodamage

    Babcock M, Mehta RC, Makino ET · J Drugs Dermatol 2015;14(1):24-30 · 2015

31. 31

    A double-blind, comparative clinical study of newly formulated retinol serums vs tretinoin cream in escalating doses: a method for rapid retinization

    Draelos ZD, Peterson RS · J Drugs Dermatol 2020;19(6):625-31 · 2020

32. 32

    A stabilized 0.1% retinol facial moisturizer improves the appearance of photodamaged skin in an eight-week, double-blind, vehicle-controlled study

    Tucker-Samaras S, Zedayko T, Cole C, et al. · J Drugs Dermatol 2009;8(10):932-6 · 2009

33. 33

    A comparison of the efficacy and safety of adapalene gel 0.1% and tretinoin gel 0.025% in the treatment of acne vulgaris: a multicenter trial

    Shalita A, Weiss JS, Chalker DK, et al. · J Am Acad Dermatol 1996;34(3):482-5 · 1996

34. 34

    A comparison of the efficacy and tolerability of adapalene 0.1% gel versus tretinoin 0.025% gel in patients with acne vulgaris: a meta-analysis of five randomized trials

    Cunliffe WJ, Poncet M, Loesche C, Verschoore M · Br J Dermatol 1998;139 Suppl 52:48-56 · 1998

35. 35

    Adapalene gel, 0.1%, as maintenance therapy for acne vulgaris: a randomized, controlled, investigator-blind follow-up of a recent combination study

    Thiboutot DM, Shalita AR, Yamauchi PS, et al. · Arch Dermatol 2006;142(5):597-602 · 2006

36. 36

    Retinoids in cosmeceuticals

    Sorg O, Antille C, Kaya G, Saurat JH · Dermatol Ther 2006;19(5):289-96 · 2006

37. 37

    Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety

    Mukherjee S, Date A, Patravale V, et al. · Clin Interv Aging 2006;1(4):327-48 · 2006

38. 38

    Retinoids: active molecules influencing skin structure formation in cosmetic and dermatological treatments

    Zasada M, Budzisz E · Postepy Dermatol Alergol 2019;36(4):392-7 · 2019

39. 39

    Guidelines of care for the management of acne vulgaris

    Reynolds RV, Yeung H, Cheng CE, et al. (AAD Work Group) · J Am Acad Dermatol 2024;90(5):1006.e1-1006.e30 · 2024

40. 40

    Retinoid or retinol?

    American Academy of Dermatology · aad.org, read 2026-09-19 · 2021

41. 41

    Retinal - Is it Better Than Retinol?

    Victoria Fu, Gloria Lu (Chemist Confessions) · chemistconfessions.com, read 2026-09-19 · 2024

42. 42

    Which is the right retinoid for me? Retinol, retinaldehyde or HPR

    Dr Sam Bunting · drsambunting.com, read 2026-09-19 · 2026

43. 43

    Retinol for newbies: a dermatologist's comprehensive guide

    Dr Shereene Idriss · dridriss.com, read 2026-09-19 · 2022

44. 44

    Retinal guide

    Medik8 · medik8.com, read 2026-09-19 · 2026

45. 45

    Your definitive guide to using retinoids

    The Ordinary (DECIEM) · theordinary.com, read 2026-09-19 · 2026

46. 46

    Retinal vs retinol: a scientific comparison

    Ingeborg van Lotringen (Get The Gloss) · getthegloss.com, read 2026-09-19 · 2024

47. 47

    Retinal (with an A): the complete guide

    Martina Trabacchi, pharmacist (ISDIN) · isdin.com, read 2026-09-19 · 2026

48. 48

    The best retinal products to smooth lines, clear breakouts and more

    Deanna Pai (NBC Select) · nbcnews.com/select, read 2026-09-19 · 2026

49. 49

    Label decode of 22 retail retinoids (this page)

    Verified Beauty Data · verifiedbeautydata.com · 2026

50. 50

    Adapalene gel 0.1% prescribing information, 8.1 Pregnancy

    U.S. FDA (DailyMed) · dailymed.nlm.nih.gov · 2024

51. 51

    Chemical stability of adapalene and tretinoin when combined with benzoyl peroxide in presence and in absence of visible light and ultraviolet radiation

    Martin B, Meunier C, Montels D, Watts O · Br J Dermatol 1998;139 Suppl 52:8-11 · 1998

52. 52

    Topical acne treatments — fact sheet

    MotherToBaby (OTIS) · mothertobaby.org · 2024