Supplements and ‘hair growth’ products

Alongside prescription medicines, customers are bombarded with information about food supplements (e.g. biotin, collagen, saw palmetto, marine proteins), caffeine-based shampoos, rosemary oil serums and castor oil.

These are all heavily promoted on social media as ‘natural’ alternatives or complementary treatments for hair loss.

Some of the most common myths are:

• Biotin supplements will fix hair loss

Biotin deficiency does cause hair loss, but genuine biotin deficiency is extremely rare in people eating a normal diet.

The evidence for biotin supplementation improving hair in people who are not deficient is not compelling. Similarly, biotin in shampoos does not penetrate to the hair follicle in any meaningful way

• Rosemary oil is as good as minoxidil

This claim is based largely on a single small, randomised trial published in 2015, which found that topical rosemary oil performed similarly to 2% minoxidil for mild androgenetic hair thinning over six months.

It is a genuine finding, but it comes from only one small study with a specific formulation of rosemary extract.

Most rosemary shampoos only contain rosemary fragrance rather than the active botanical extract, so the mention of the ingredient on the label does not guarantee the mechanism in the product

• Caffeine shampoos stimulate hair growth

In vitro (laboratory) studies have shown that caffeine can stimulate hair follicle cells, but translating that into meaningful clinical benefit in a shampoo that is rinsed off within minutes is a different matter.

A 2025 systematic review of clinical trials of topical caffeine preparations found limited and mixed evidence, with the overall quality of evidence rated low. Caffeine shampoos are unlikely to cause harm but are not a hair loss treatment

• Hats and tight hairstyles cause permanent hair loss

Wearing hats does not cause hair loss. However, traction alopecia – caused by repeatedly wearing very tight hairstyles such as high ponytails, cornrows or braids over many years – is a recognised and increasingly common form of hair loss, particularly in women.

Unlike androgenetic alopecia, traction alopecia can sometimes be reversed if caught early and the hairstyle changed.