Does onion juice increase hair growth?

Question

Some web-sites say that onion juice, applied topically, can promote hair growth

Is this true?

Closely related question: Does garlic improve hair growth in androgenetic alopecia?

Answer 1

There are a great many quirky cures spread all over the internet and most of them have no evidence besides a series of bloggers boasting their benefits.

In this case however, it seems we might have a slight exception. In 2002, Sharquie K1, Al-Obaidi HK published a piece of research in the Journal of Dermatology called 'Onion juice (Allium cepa L.), a new topical treatment for alopecia areata' whereby they saw significant hair regrowth in patients suffering from alopecia when treated with topical (applied to the skin) onion juice.

*The article is publicly available (link corrected) as an abstract, and it seems from a quick glance that the research had fairly decent methodology despite a few obvious faults. It was single blinded and placebo-controlled, but there was no randomization of participants and the study only included 63 participants and the control group was much smaller than the intervention group. The placebo used was water, and as such wouldn't have had an even similar consistency or colour to the onion juice, which could have skewed the results.

All that said, the results were quite significant. (P<0.0001)

Now, the reason I haven't just said "Yes, it does work" is because we have some things to consider. Firstly, the study has not been reproduced. There are no records of this being done again, which begs the question why? Publication bias means that if this was repeated and put into question we probably wouldn't have heard about it. Also, it was used to treat alopecia, which is a rare cause of hair loss. Male pattern baldness (the most common cause) was not tested. Also, chronic and severe cases were excluded which suggests the participants of this study were already very likely to improve regardless of treatment. The lack of randomization in this case is a real issue.

So, in conclusion; Unless you have recent onset mild or moderate alopecia there is no reason at all to suspect that this might work. If you do have mild or moderate recent onset alopecia then there is a possibility it might work, but I wouldn't get your hopes up given there is only one piece of moderate, unrepeated research on a low number of participants.