Biotin: Haircuts Plus Health Advice?

A friend asked me, “What do you know about biotin?”

I said, “Not much. Why do you ask?”

She explained that the woman who cuts her hair at the hair salon recommended she take biotin to strengthen her nails and improve hair growth. She tried it, and within a couple of months, her nails looked better than they ever had in her whole life: the ridging was gone and they were no longer splitting or bending. And her hair, which had begun to thin, was noticeably thicker again.

I know what you’re going to say: this is nothing but a testimonial, and she could have been mistaken: post hoc ergo propter hoc and all that. Hair salons are not reliable sources of health advice, and perhaps not even a very reliable source of hair advice. I am leery of their recommendations for expensive shampoos and gimmicky conditioners. They offer things I don’t want, like hair coloring (I consider my gray hairs hard-earned badges of honor), waxing, eyebrow arch threading, scalp massage, and facials. Some of them have tanning beds in a back room. Incredibly, several of them in my area even offer ear candling!

I’m frequently asked to look into the evidence for various diet supplement products, and I’m almost always disappointed. The company websites offer little but claims and testimonials. There may not be a tab for “scientific studies” and if there is, the studies gathered there are often a farce, and may not even pertain to the product in question.

This time I was pleasantly surprised. The trustworthy Natural Medicines Comprehensive Database rated biotin “likely effective” for biotin deficiency and described preliminary evidence that biotin might increase the thickness of fingernails and toenails in people with brittle nails, although it considered that the evidence was insufficient to rate.

What is biotin?

Biotin is one of the B complex vitamins, sometimes known as vitamin B7 or vitamin H. The B complex vitamins are needed for healthy skin and hair. Biotin is produced in the intestines by bacteria and is also found in the diet. The mechanism of action and metabolism have been studied. Biotin is water soluble and its elimination half-life is slightly less than 2 hours, so you can’t build up a store of it. Biotin deficiency in humans is rare, but it can cause thinning of the hair, frequently with loss of hair color, and red scaly rash around the eyes, nose, and mouth. It can even lead to depression, lethargy, hallucinations, and paresthesias of the extremities. Deficiency is most likely in congenital biotinidase enzyme deficiency, malabsorption syndromes, and in long term parenteral nutrition. Other things that can deplete biotin are eating two or more raw egg whites daily over long periods, excess alcohol consumption, certain anti-seizure medications, and possibly diabetes and cigarette smoking.

The NMCD rates it as “likely safe.” It is well tolerated in doses of 10 mg per day. Only one severe reaction has been reported, and it has not been definitely linked to biotin. A dermatologist writing in the Huffington Postargues that the role of biotin is not totally clear, and users should avoid overdosing. He recommends 2.5 mg (2500 mcg) a day, but that isn’t based on hard evidence. Some supplements contain as much as 5000 or 10,000 mcg.

The evidence

On to PubMed…where I actually found 3 positive human clinical studies of subjects with brittle nails and no negative ones. A study of 35 patients who took daily biotin found that 22 showed clinical improvement and 13 reported no change in their condition. A small study in Switzerland used scanning electron microscopy to study whether favorable clinical results could be corroborated. Indeed, they were able to measure a 25% increase in the thickness of nails with biotin supplementation. In another study 45 patients were evaluated: 91% showed definite improvement and none of the patients considered the treatment altogether ineffective. At least one website calls the evidence “very weak.” Others consider it to be stronger.

There is good evidence from animal studies: biotin has been shown to improve hoof health, prevent lameness, and improve milk production in dairy cows. It has also been shown effective in Lipizzaner horses, ponies, and swine.

Is it worth trying?

If you have brittle nails, it might be worth a try. The evidence is consistently positive, albeit only from three small preliminary trials that have not been replicated. I don’t usually recommend using a medication until the evidence is much stronger than that. However, in this case I think there are good arguments for trying it:

  • There is a plausible mechanism.
  • There is supporting evidence from animal studies.
  • The human studies are not just based on subjective reports of improvement: one of them used objective measurements with electron microscopy and demonstrated a 25% increase in nail thickness.
  • It is safe.
  • There are no other good evidence-based treatment options. Horsetail, moisturizers, nail protection, gelatin and other remedies have been tried, but they haven’t been proven effective. So with the existing evidence, biotin is probably the treatment of choice.
  • I think the existing evidence justifies a therapeutic trial of biotin for brittle nails. If you haven’t improved after 6 months, you can stop taking it. A 3 month supply can cost as little as $4.19, so there is little to lose.


Brittle nails are a relatively minor item in the general scheme of things; but I’m glad I looked into biotin, and I think my experience offered a lesson applicable to other questions. The fact that Dr. Oz recommends biotin for hair loss made me very suspicious (what is the opposite of the “appeal to authority” fallacy?), and I was prejudiced against using a hair salon as a source of information. I was predisposed to reject biotin. But I was aware of that and I made an effort not to let my bias interfere with my judgment about the evidence. Even if a source is untrustworthy, it would be foolish to reject a claim before examining the evidence just as carefully as we would for any other claim. I certainly don’t recommend going to a hair salon for your medical advice, any more than I would recommend going to a doctor for a haircut; but it would be a mistake to assume that everything you hear there is wrong. In this case, the beautician got it right; you might say she nailed it. (pun intended)

This article was originally published in the Science-Based Medicine blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

Scroll to top