Does retinol improve scalp health or help other hair growth treatments work?

Retinol, known primarily for its benefits on facial skin, is drawing increasing attention for its effects on the scalp. When applied to the scalp, retinol is converted by the body into retinoic acid, a biologically active molecule that influences cellular growth, differentiation and communication. This article looks at what is known about retinol and retinoic acid on the scalp, and whether they change the response to treatments such as minoxidil. One point matters from the start: every study below used all-trans retinoic acid (tretinoin), a prescription medicine, mostly on hair follicles in the lab or in mice. No trial has tested over-the-counter retinol for hair.

Retinol and Cellular Renewal in the Scalp

Retinoids speed up epidermal turnover on facial skin, and it is often claimed that this helps remove dead skin cells and residues that accumulate on the scalp. The claim is that the outermost layer of the skin, the stratum corneum, can become compacted due to oil production, styling products and pollution. It is also claimed that a dense layer hinders nutrients and oxygen reaching the hair follicle; this has not been shown.

In theory, faster renewal could leave a cleaner scalp surface. This has not been measured for retinol on the scalp, and retinoids commonly cause redness, dryness and peeling.

Activation of Hair Follicle Stem Cells

A study published in the Journal of the European Academy of Dermatology and Venereology (Wen et al., 2025, online 2024) investigated the effects of retinoic acid on human and mouse hair follicles. Researchers used microdissected human scalp follicles and also worked with mouse follicles in the resting (telogen) phase. They found that retinoic acid stimulated hair follicle stem cells and promoted transition into the active growth phase, known as anagen. The activation was associated with the Wnt/β‑catenin signaling pathway, which plays a central role in controlling whether hair follicles remain at rest or begin producing new hair fibers.

This is laboratory and animal work. The authors also report a clinical study of 60 people with androgenetic alopecia who used 0.025% tretinoin cream or 5% minoxidil for six months, with no placebo group. Hair counts rose from baseline in the first month with tretinoin, and at six months there was no significant difference between the groups. This does not show that tretinoin works as well as minoxidil, or that over-the-counter retinol has any effect.

Enhancement of Other Hair‑Growth Treatments

Minoxidil is one of the most frequently prescribed topical treatments for pattern hair loss. Retinoic acid has been studied as a potential enhancer of minoxidil’s effects. A 2007 study on human hair follicles grown in vitro (Kwon et al.) found that combining minoxidil with all‑trans retinoic acid resulted in greater hair growth than minoxidil alone. It also looked at molecular activity related to cell survival and growth. The combination increased phosphorylation of the Erk and Akt pathways, which are associated with cellular proliferation and longevity, and also increased the ratio of Bcl‑2 to Bax, a marker suggesting reduced programmed cell death.

These are laboratory results in cultured follicles and cells. They do not show that the combination works better in people.

A report published in 1986 (Bazzano et al.) described 56 people with androgenetic alopecia treated for one year with topical tretinoin alone or combined with 0.5% minoxidil. The authors reported some regrowth in about 58% of people with tretinoin and terminal hair regrowth in 66% with the combination. This was an uncontrolled, preliminary report, and the authors called for more research.

In the one randomized trial found, 31 men used either 5% minoxidil twice daily or 5% minoxidil plus 0.01% tretinoin once daily. Both groups gained hair, with no significant difference between them, and itch or irritation occurred in 4 of 14 vs 5 of 15. The trial was too small to show the two regimens are equally effective or equally well tolerated. The trial did not show that adding tretinoin gives extra regrowth (Shin et al. 2007).

It is often said that retinoic acid helps minoxidil by increasing skin permeability. This has not been measured for retinol on the scalp. Topical retinoids thicken the epidermis rather than thinning it (Rittié et al. 2006). A 2019 study proposed a different mechanism: 5 days of topical tretinoin raised levels of the follicle enzyme (sulfotransferase) that activates minoxidil. On an enzyme test, 43% of people predicted not to respond to minoxidil were reclassified as predicted responders. Hair growth was not measured (Sharma et al. 2019).

Retinoids also irritate the skin, and combining them with other strong products can add to that irritation.

Evidence of Potential Negative Effects

Retinoic acid is not universally beneficial and can induce negative outcomes under certain conditions. A 2005 study (Foitzik et al.) using human scalp follicles grown in vitro found that exposure to retinoic acid at concentrations of 10⁻⁸ to 10⁻¹⁰ M resulted in premature entry into the catagen phase, which is the regression stage of the follicle cycle. About 80% of treated follicles were in a catagen-like stage by day six, compared with 30% of untreated follicles. The response was associated with increased expression of transforming growth factor‑beta 2 in the dermal papilla. TGF‑β2 is known to push follicles toward regression. These were low concentrations in cultured follicles, not the scalp, but they show retinoic acid can have the opposite of the desired effect.

Taken together, these lab findings suggest that retinoic acid can both activate and suppress follicle growth, depending on conditions that have not been worked out for the human scalp. This duality is not unique to retinoic acid, but it means that the dose, frequency of application and the biological context of the scalp matter.

What We Need to Know as Patients

**When evaluating whether to use retinol or retinoic acid on the scalp, the most important takeaway is that the compound does not act uniformly. ** Lab studies suggest it may increase cellular activity and help follicles re‑enter the anagen phase, but they also show it can induce regression. The evidence comes from prescription tretinoin, not over-the-counter retinol, and there is no agreed safe dose for the scalp.

For androgenetic alopecia, these findings are early. The one small randomized trial (31 men) found no significant difference in regrowth between once-daily minoxidil plus tretinoin and twice-daily minoxidil; it was too small to show whether tretinoin adds anything. Conversely, if excessive concentrations push follicles toward catagen, some users may find hair shedding increases rather than decreases.

Safety. Tretinoin is a prescription medicine; discuss it with a prescriber before using it on the scalp. Oral isotretinoin causes severe birth defects and is contraindicated in pregnancy (US label boxed warning). It can also cause hair loss, which sometimes persists (DailyMed, Amnesteem label). For topical retinoids, a meta-analysis of 654 exposed pregnancies found no statistically significant rise in major birth defects (odds ratio 1.22, 95% CI 0.65–2.29), but the authors say it was too small to show that using them in pregnancy is safe (Kaplan et al. 2015). People who are pregnant, trying to conceive or breastfeeding should not use retinoids on the scalp without medical advice.

Retinol and its active metabolite retinoic acid exert multiple biological effects on the scalp. In lab studies, retinoic acid affects epidermal turnover and hair follicle stem‑cell activity; effects on the absorption of other treatments have not been shown for retinol.

Laboratory studies suggest that retinoic acid can both support and suppress hair follicle growth, depending on dose and exposure. Human evidence is limited to an uncontrolled 1986 report, a 60-person comparison of tretinoin with minoxidil without a placebo group (Wen et al.), and one small randomized trial (31 men) that found no significant difference between once-daily minoxidil plus tretinoin and twice-daily minoxidil.

No study has tested over-the-counter retinol for hair loss. Anyone considering a topical retinoid for the scalp should discuss it with a doctor, especially if pregnant or planning a pregnancy.

References

Wen, L., Fan, Z., Huang, W., et al. (2025). Retinoic acid drives hair follicle stem cell activation via Wnt/β‑catenin signalling in androgenetic alopecia. Journal of the European Academy of Dermatology and Venereology, 39(1), 189–201. Retrieved from https://pubmed.ncbi.nlm.nih.gov/38629345/

Kwon, O. S., Pyo, H. K., Oh, Y. J., et al. (2007). Promotive effect of minoxidil combined with all‑trans retinoic acid (tretinoin) on human hair growth in vitro. Journal of Korean Medical Science, 22(2), 283–289. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17449938/

Bazzano, G. S., Terezakis, N., & Galen, W. (1986). Topical tretinoin for hair growth promotion. Journal of the American Academy of Dermatology, 15(4 Pt 2), 880–883. Retrieved from https://pubmed.ncbi.nlm.nih.gov/3771854/

Shin, H. S., Won, C. H., Lee, S. H., et al. (2007). Efficacy of 5% minoxidil versus combined 5% minoxidil and 0.01% tretinoin for male pattern hair loss: a randomized, double‑blind, comparative clinical trial. American Journal of Clinical Dermatology, 8(5), 285–290. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17902730/

Rittié, L., et al. (2006). Retinoid‑induced epidermal hyperplasia is mediated by epidermal growth factor receptor activation via specific induction of its ligands heparin‑binding EGF and amphiregulin in human skin in vivo. Journal of Investigative Dermatology, 126(4), 732–739. Retrieved from https://pubmed.ncbi.nlm.nih.gov/16470170/

Sharma, A., Goren, A., Dhurat, R., et al. (2019). Tretinoin enhances minoxidil response in androgenetic alopecia patients by upregulating follicular sulfotransferase enzymes. Dermatologic Therapy, 32(3), e12915. Retrieved from https://pubmed.ncbi.nlm.nih.gov/30974011/

Foitzik, K., Spexard, T., Nakamura, M., Halsner, U., & Paus, R. (2005). Towards dissecting the pathogenesis of retinoid‑induced hair loss: all‑trans retinoic acid induces premature hair follicle regression (catagen) by upregulation of transforming growth factor‑beta2 in the dermal papilla. Journal of Investigative Dermatology, 124(6), 1119–1126. Retrieved from https://pubmed.ncbi.nlm.nih.gov/15955085/

Kaplan, Y. C., Ozsarfati, J., Etwel, F., et al. (2015). Pregnancy outcomes following first‑trimester exposure to topical retinoids: a systematic review and meta‑analysis. British Journal of Dermatology, 173(5), 1132–1141. Retrieved from https://pubmed.ncbi.nlm.nih.gov/26215715/

DailyMed. Amnesteem (isotretinoin capsules) prescribing information. Retrieved from https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b2cb63c9-f825-4991-9a2c-6260f1bbcc2c