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Other actives

Caffeine

Also listed as 1,3,7-trimethylxanthine

Stimulates hair follicles in a dish and reaches them from a shampoo, but proof that caffeine products slow hair loss in people is thin. Eye-cream claims are weaker still.

Weak evidenceTypical strength: About 0.2-1% in hair tonics and shampoos; up to a few percent in eye products

What it is

In hair products, caffeine is meant to counter the hormone-driven shrinking of follicles in pattern hair loss. It does reach follicles quickly from a shampoo, and it stimulates growth in follicles kept alive in a dish.

In eye creams and serums, caffeine is marketed to reduce puffiness and dark circles by narrowing blood vessels. That is plausible, but there is little trial evidence and any effect is short-lived.

How strong is the evidence?

Weak evidence

Lab studies show caffeine stimulates human hair follicles in culture, and a pharmacokinetic study shows it enters follicles within 2 minutes of shampooing. The only sizeable clinical trial (210 men) was open-label, had no placebo arm, and found a 0.2% leave-on caffeine liquid 'non-inferior' to 5% minoxidil on a growing-hair ratio, not hair count. No placebo-controlled trial shows caffeine shampoo reduces hair loss.

What it's used for, checked

Slows pattern hair loss (leave-on)

Unproven

One open-label trial without placebo; needs independent confirmation.

Slows hair loss (shampoo)

Unproven

Caffeine reaches follicles, but no trial shows a benefit from rinse-off use.

Reduces under-eye puffiness

Unproven

Plausible short-term vasoconstriction; little clinical evidence.

Dark circles

Unproven

Circles caused by pigment or thin skin won't respond.

Cellulite

Unproven

Promotes fat breakdown in lab studies; no convincing trials of visible change.

Who should be careful

  • Topical caffeine is generally well tolerated; the amount absorbed is small.
  • For progressing pattern hair loss, the proven options are minoxidil and (for men) finasteride; see a clinician rather than relying on caffeine products.
  • Sudden, patchy or rapid hair loss needs medical assessment.

The studies

Every citation is checked against its PubMed record.

  1. Effect of caffeine and testosterone on the proliferation of human hair follicles in vitro.
    Fischer TW, Hipler UC, Elsner P · Int J Dermatol · 2007 · Laboratory study (cultured follicles)

    In hair follicles taken from men with pattern hair loss and grown in a dish, caffeine at 0.001-0.005% counteracted testosterone's growth suppression and stimulated hair shaft growth on its own.

  2. Follicular penetration of topically applied caffeine via a shampoo formulation.
    Otberg N, Teichmann A, Rasuljev U, et al. · Skin Pharmacol Physiol · 2007 · Human pharmacokinetic study

    Caffeine from a shampoo left on for 2 minutes reached the blood, entering faster via hair follicles than through the skin surface. Shows delivery is possible, not that it grows hair.

  3. An Open-Label Randomized Multicenter Study Assessing the Noninferiority of a Caffeine-Based Topical Liquid 0.2% versus Minoxidil 5% Solution in Male Androgenetic Alopecia.
    Dhurat R, Chitallia J, May TW, et al. · Skin Pharmacol Physiol · 2017 · Open-label RCT (non-inferiority)

    210 men used a 0.2% caffeine leave-on liquid or 5% minoxidil for 6 months; the share of growing-phase hairs rose by 10.6% and 11.7% respectively, and caffeine was judged non-inferior. Open-label, no placebo, and a trichogram rather than hair-count endpoint.

  4. Caffeine's mechanisms of action and its cosmetic use.
    Herman A, Herman AP · Skin Pharmacology and Physiology · 2013 · Review

    Reviews caffeine's skin penetration and cosmetic uses, noting topical products usually contain about 3%: fat breakdown in anti-cellulite products, antioxidant and UV-protective effects, increased microcirculation and hair-growth stimulation, largely from lab data.