Does Onion Water Support Hair Health?
Dr. Echeverry says she’s repeatedly heard about the practice from clients from cultures where it had long been part of family tradition.
“In my practice in Florida, where we see a very diverse background of hair loss clients, I used to service people of North African, Pakistani, and Indian descent who through their hair loss journey would rediscover onion juice as a secret to healthy hair by talking to their mothers, grandmothers, or through the advice of Ayurvedic medicine practitioners when they would go back to their home countries to visit,” she says.
Many associated it with thick, healthy hair. Still, the experts note that tradition and anecdotes are not the same as strong clinical evidence.
Gaunitz says claims about onion water’s benefits for the hair “hold validity to a degree.” But he doesn’t unconditionally support the practice because it’s subject to a random recipe with a variety of variables that may or may not work from person to person.
It’s the sulfur — the same compound that gives onions their pungent smell — that may make it helpful in growing healthy hair, he says. Gaunitz notes that some dermatological treatments use sulfur, which is known for its anti-inflammatory and antimicrobial effects and may help support scalp health in some people.
“The sulfur content of onion water is very high,” says Gaunitz. (You’ll also find high levels of sulfur in other foods, including meat, eggs, cruciferous veggies, and other alliaceous veggies, like garlic.)
That matters because healthy hair starts with the scalp. “If you are able to reduce that overall inflammation, you are going to typically have a more dense, robust hair with more body,” Gaunitz says. Inflammation can chip away at structures in the follicle involved in hair recovery and pigment maintenance, he explains, so calming scalp inflammation may help support healthier-looking hair overall.
What Does Research Say About Onion Water and Hair Growth?
While limited high-quality research has examined how these properties translate to the scalp, one review of the medical literature notes the antifungal and antimicrobial potential of onion extract and onion essential oils. However, these often contain higher concentrations of active ingredients than whole onions.
Some of these recent claims derive from a small study published in 2002 comparing the effects of onion juice and tap water on hair growth in individuals with alopecia areata, a specific genetic condition that causes hair loss.
Researchers found that applying onion juice twice daily was associated with signs of hair regrowth in nearly 87 percent of participants. Of the 23 participants who used onion juice, 20 reported regrowth by six weeks into the trial, whereas only 2 participants in the tap water group reported the same.
However, it’s unclear whether these findings apply to healthy hair or to people with hair loss unrelated to health problems. The study’s small sample size also means further research is necessary to fully understand this potential effect.
Echeverry notes the study was also an unblinded trial. This means that because participants knew whether they were applying onion juice or tap water, the placebo effect may have influenced the results, she says.
Atilola Moronfolu, a certified trichologist in Houston, says onion water may be more helpful for length retention than true hair growth. “It’s not going to increase the hair growth rate,” she says. “It’s just going to make sure that you retain a lot of the hair you would have grown anyway by helping reduce breakage.”
Take note, though: Onion water won’t work for all types of hair loss, such as hair loss caused by nutrient deficiencies and androgenetic alopecia (male pattern baldness), says Gaunitz. There’s no research to suggest that onion juice could suppress levels of a hormone called dihydrotestosterone that has possible links to shrinking hair follicles. Likewise, it hasn’t been shown to increase vitamin D levels at the base of the hair follicle, for example, which could help address nutrition-related hair loss.
Think of it as a form of support rather than a treatment. “This isn’t something that is going to replace finasteride or minoxidil. It’s simply going to anecdotally improve the overall health of the scalp,” Gaunitz says. He suggests this might encourage healthier, thicker hair in people dealing with scalp-related issues.
Echeverry agrees. Hair loss is often multifactorial, and DIY hacks can distract people from getting an accurate diagnosis and evidence-based care, she says.
If you’re concerned about the hair or skin effects of nutritional deficiencies or alopecia areata, consult a certified dermatologist or trichologist.
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