Caffeine Shampoo vs Minoxidil: What the Head-to-Head Study Did and Didn't Show

By the Minoxidil Quick editorial team · researched from published studies and FDA labeling; not reviewed by a clinician

One randomized trial is behind most claims that caffeine is as good as minoxidil. It is a real study with real limits, and it didn’t test a shampoo.

Short answer: the head-to-head trial compared a leave-on caffeine liquid, not a shampoo, with 5% minoxidil solution in 210 men for six months. It concluded the caffeine liquid was “not inferior” on one lab measure, the proportion of hairs in the growth phase. The study was open-label (everyone knew what they were using), had no placebo group, and was funded by the company that makes the caffeine product. It’s interesting evidence, not proof that a caffeine shampoo can replace minoxidil.

The study in brief

The trial was published in Skin Pharmacology and Physiology by Dhurat and colleagues. Here is what it did, from the paper itself:

What it found

In the per-protocol group, the anagen ratio improved by 11.68% on minoxidil and 10.59% on caffeine. The difference, 1.09 percentage points, had a 95% confidence interval of −2.72 to 4.89, which sits inside the 5-point margin the authors set in advance. On that basis they concluded the caffeine liquid “should be considered as not inferior” to 5% minoxidil in men with androgenetic alopecia. The intention-to-treat analysis showed a similar picture. Side effects were minimal: one person in the minoxidil arm reported a mild headache, judged unrelated to treatment.

What it didn’t show

1. It didn’t measure visible hair

The anagen ratio is the share of plucked or sampled hairs that are in the growth phase. It’s a reasonable biological signal, but it isn’t hair count, hair thickness or how full your hair looks. Trials that support minoxidil’s approval used hair counts in a defined scalp area. A treatment can nudge the growth-phase ratio without producing the same visible change, and this study can’t tell us whether it did.

2. There was no placebo

Both groups improved. Without a third group using an inactive liquid, we can’t tell how much of either improvement came from the products versus natural variation, seasonal shedding, or the extra attention people pay to their scalp in a trial.

3. Everyone knew what they were using

Open-label designs are cheaper and simpler, but they leave room for bias in how participants follow the routine and, depending on how measurements are handled, how outcomes are assessed.

4. The sponsor made the product

Industry funding doesn’t make results wrong, and the authors disclosed it. It does mean this result needs independent replication before it carries much weight, and as far as we found, the caffeine-versus-minoxidil comparison rests largely on this one trial.

5. Only men, only six months

The study enrolled men with moderate pattern loss. It says nothing about women, about advanced loss, or about whether the effect lasts beyond six months.

6. It wasn’t a shampoo

This is the big one for shoppers. The caffeine product in the trial was a liquid applied twice a day and left on the scalp, the same way the minoxidil was. A shampoo is lathered, left for a short time and rinsed off. The study tells you nothing directly about how much caffeine a rinse-off shampoo delivers to the follicle.

Why contact time matters

Topical treatments work only if enough active ingredient reaches the follicle and stays there long enough. A leave-on solution sits on the scalp for hours. A shampoo is in contact for the length of a wash, then mostly goes down the drain. Some caffeine may stay behind in the follicle openings, but a rinse-off product and a twice-daily leave-on liquid are not the same dose, and assuming they are is where most marketing goes wrong.

If you do use a caffeine shampoo, the most a reasonable reading of the evidence supports is: follow the product’s instructions about how long to leave it on, use it consistently, and don’t drop a treatment with stronger evidence to make room for it.

Can you use both?

Generally, yes. A caffeine shampoo used to wash the scalp doesn’t conflict with minoxidil applied to a dry scalp afterwards, and many people already wash with something. The practical issues are irritation and routine:

• If your scalp gets red or itchy, the minoxidil label says to stop and ask a doctor. Adding a new product makes it harder to tell what caused it, so introduce one change at a time.
• Apply minoxidil to a dry scalp, after washing rather than before, so you don’t rinse it away. Our guide to layering minoxidil with other hair products covers timing.
• A caffeine shampoo is not a replacement for minoxidil, finasteride or any prescription your clinician recommends.

How to read the next “as good as minoxidil” claim

Caffeine isn’t the only ingredient marketed this way. Rosemary oil, peptides, plant extracts and various serums have all been described as rivals to minoxidil. You can test any of those claims with the same questions this trial raises:

• Was there a placebo group? Without one, improvement in both arms tells you little about either product.
• Was it blinded? If participants and assessors knew who used what, expectations can shape the result.
• What was measured? Hair counts and standardized photos are closer to what you care about than growth-phase ratios or self-reported satisfaction.
• How long did it run? Six months is a minimum for hair; a year tells you more.
• Who paid? Industry funding is common and disclosed in good papers. It raises the bar for independent replication.
• Is the product you’re buying the one that was tested? Same ingredient, same concentration, same format, same contact time?
• Was it noninferiority or superiority? “Not inferior within a margin” is a narrower claim than “as good as,” and the choice of margin matters.

A product that fails several of these isn’t necessarily useless, but it hasn’t earned the comparison its marketing makes.

How caffeine compares with the evidence for minoxidil

Minoxidil has FDA approval for pattern hair loss in men and women, based on placebo-controlled trials, and decades of use. Caffeine has one notable industry-funded noninferiority trial of a leave-on liquid, plus lab and absorption studies. That doesn’t make caffeine useless; it makes it a much less certain bet. Our review of minoxidil alternatives rates caffeine shampoo alongside rosemary oil, lasers and other options, and our myths article covers other claims that outrun their evidence.