Which Hair Ingredients Actually Work?
Not every haircare ingredient works in the same way. Some support hair growth, others help protect the follicle from oxidative stress, and a few are involved in pigment production itself. The strongest ingredients have a clear biological mechanism — not just marketing claims.
Here is what the research shows for five common ingredients, including two that reach into color.
Does caffeine actually help hair grow?
Caffeine: keeping the growth phase going
Each follicle cycles between a growth phase, anagen, and a resting phase. The longer a follicle stays in anagen, the longer it continues producing a hair strand.
Research using cultured human hair follicles has shown that caffeine can counteract testosterone-induced growth suppression and stimulate hair shaft elongation in vitro.¹
The important distinction is delivery. Drinking coffee doesn't send caffeine directly to your hair follicles in the same way as a topical product. Scalp formulations are designed to deliver ingredients locally, where the follicles are located.
Does rosemary oil really work?
Rosemary: protecting the environment, and the color
Rosemary is one of the better-studied botanical ingredients used in haircare.
Compounds found in rosemary, including carnosic acid and ursolic acid, have been studied for antioxidant and anti-inflammatory activity.²
In a six-month randomized comparative trial involving people with androgenetic alopecia, both rosemary oil and 2% minoxidil groups experienced a significant increase in hair count at six months, with no significant difference in hair count between the groups. Scalp itching was reported more frequently in the minoxidil group.³
Its role in hair pigmentation is less established, but there is a biological rationale for studying it. Oxidative stress is a well-documented contributor to the biology of hair graying.⁴
A 2025 cross-sectional study also found an association between rosemary use and lower self-reported hair graying. However, because the study was observational, it cannot establish that rosemary prevented or reduced graying.⁵
What does rice bran do for hair?
Rice bran: a nudge toward the growth signal
Rice bran mineral extract doesn't act on the hair shaft itself. Research has investigated its effects on the dermal papilla, a group of cells at the base of the follicle involved in regulating hair growth.
In cultured human dermal papilla cells, rice bran mineral extract increased the expression of molecules associated with the anagen growth phase and activated the Wnt/β-catenin pathway. The researchers also observed effects on inflammatory signaling.⁶
This is isolated-cell evidence rather than a human clinical trial, so it points to a potential biological mechanism rather than proving that rice bran will increase hair growth in people.
Is tyrosine important for hair color?
Tyrosine: purely about color
Yes, but not in the way people sometimes assume.
Melanin is produced by melanocytes through a series of biochemical reactions. Tyrosinase, a key enzyme in melanogenesis, catalyzes the initial reactions involving the amino acid tyrosine.⁷
That makes tyrosine part of the raw material used in pigment production.
However, that does not mean adding more tyrosine will automatically produce more pigment. Whether additional tyrosine increases hair pigmentation in a healthy follicle has not been established. Its biological relevance is as a building block in melanogenesis, not as a proven treatment for gray hair.⁷
Do vitamins help?
Vitamins: cofactors, not magic
Nutritional deficiencies can contribute to some forms of hair loss. Research has examined nutrients including vitamin D, iron, zinc and B vitamins in relation to hair health and hair-loss conditions.⁸
When a genuine deficiency exists, identifying and correcting it may be important. But for people without a deficiency, evidence supporting routine supplementation for hair growth is limited. For example, there is little evidence supporting biotin supplementation in otherwise healthy individuals without a deficiency.⁸
Think of vitamins and minerals as part of the conditions required for normal biology rather than a shortcut to better hair.
The point
Not every ingredient is trying to achieve the same outcome.
Caffeine has been studied for its effects on hair growth in human follicles.¹ Rice bran mineral extract has shown effects on growth-related signaling pathways in dermal papilla cells.⁶ Tyrosine is a substrate involved in melanin production.⁷ Rosemary contains compounds with antioxidant and anti-inflammatory properties and has also been clinically studied in androgenetic alopecia.² ³
An ingredient is only as useful as the biological job it can perform — and the evidence supporting it.
Specificity is the difference between a formula and a wish.
References
1. Fischer TW, Hipler UC, Elsner P. Effect of caffeine and testosterone on the proliferation of human hair follicles in vitro. International Journal of Dermatology. 2007;46(1):27–35. DOI: 10.1111/j.1365-4632.2007.03119.x
2. de Macedo LM, Santos ÉMD, Militão L, Tundisi LL, Ataide JA, Souto EB, Mazzola PG. Rosemary (Rosmarinus officinalis L., syn Salvia rosmarinus Spenn.) and Its Topical Applications: A Review. Plants. 2020;9(5):651. DOI: 10.3390/plants9050651
3. Panahi Y, Taghizadeh M, Marzony ET, Sahebkar A. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed. 2015;13(1):15–21. PMID: 25842469
4. Seiberg M. Age-induced hair greying: the multiple effects of oxidative stress. International Journal of Cosmetic Science. 2013;35(6):532–538. DOI: 10.1111/ics.12090
5. Aldhafiri HJ, Alshalhoob H, Alshreef SM, et al. Hair greying associated with rosemary use: a cross-sectional study in Saudi Arabia. Dermatology Reports. 2025. DOI: 10.4081/dr.2025.10126
6. Kim YM, Kwon SJ, Jang HJ, Seo YK. Rice bran mineral extract increases the expression of anagen-related molecules in human dermal papilla through Wnt/β-catenin pathway. Food & Nutrition Research. 2017;61(1):1412792. DOI: 10.1080/16546628.2017.1412792
7. Fernandes B, Cavaco-Paulo A, Matamá T. A Comprehensive Review of Mammalian Pigmentation: Paving the Way for Innovative Hair Colour-Changing Cosmetics. Biology. 2023;12(2):290. DOI: 10.3390/biology12020290
8. Almohanna HM, Ahmed AA, Tsatalis JP, Tosti A. The Role of Vitamins and Minerals in Hair Loss: A Review. Dermatology and Therapy. 2019;9(1):51–70. DOI: 10.1007/s13555-018-0278-6
