Can Onion Water Help Keep Your Hair Healthy?

In the pursuit of lustrous, healthy hair, many people turn to herbal remedies to support their washing or nourishing routine. Among these is onion water or juice — either the water you boil onions in, a blended juice mix including onions, or the addition of diced onions to shampoo.

William Gaunitz, a certified trichologist (hair and scalp expert) and founder of Advanced Trichology in Laguna Beach, California, says his clients have discussed this natural treatment for years.

The remedy has been around for generations, according to Andrea Echeverry, PhD, a microbiologist, immunologist, and immediate past president of the Association of Professional Trichologists, who is based in Davie, Florida. But how does this tradition stack up against scientific studies?

Learn about the benefits and drawbacks of onion water for hair health, the best recipes to use, and why there’s more to the humble onion than meets the eye (or follicle).

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.

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?

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.

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.”

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.

What Are the Potential Side Effects of Onion Water for Hair?

Even if you’re not allergic to onions, onion water is not necessarily risk-free.

Then there is the smell. Gaunitz says odor is one of the biggest practical drawbacks. In his experience, clients who used onion or garlic preparations would often apply the mixture at night, massage it into the scalp, and cover their hair with a shower cap because the smell was so strong.

There’s also the issue of consistency and long-term use. According to Gaunitz, repeatedly applying DIY mixtures to the scalp may alter the scalp microbiome, the community of bacteria living on your scalp, in ways that aren’t always beneficial.

If a treatment is unpleasant, difficult to maintain, or not something a person would realistically use long term, that limits its usefulness in the first place.

How to Use Onion Water for Healthy Hair

If you’re interested in trying onion water, experts say it’s better to approach it cautiously and not as a substitute for proper diagnosis or proven therapies.

Gaunitz advises against cooking or boiling the onions. “The [theoretical] medicinal properties come from the raw onion itself,” he explains.

Based on what Gaunitz has heard from clients, a typical DIY version involves these steps:

1. Blend a whole onion with water.
2. Let the mixture sit overnight.
3. Strain it through a cheesecloth so only the liquid remains.
4. Apply that liquid directly to the scalp, often with a dropper bottle.
5. Massage it in.
6. Leave it on for a period before washing it out.

1. Peel and chop three to four onions into small pieces.
2. Extract the juice by squeezing or blending them.
3. Apply the juice to your scalp using a cotton pad.
4. Massage it into the scalp, leave it for an hour, then rinse. Follow with a second cleanse of your usual shampoo.

But Echeverry doesn’t recommend adding onion juice to shampoo or conditioner. Doing so can disrupt a product’s pH, viscosity, stability, and preservation system, potentially introducing contamination and changing how the product performs, she says.

If someone wants to test the trend, she says it would be best to do so under the guidance of a professional who can monitor scalp health and hair changes over time, rather than relying on guesswork.

Hair-Healthy Alternatives to Onion Water

If your goal is healthier hair, experts say you don’t need to rely on a DIY remedy.

Gaunitz advises focusing first on the cause of the problem. If hair loss is potentially related to inflammation, hormones, nutrition, or another underlying issue, it requires a direct diagnosis and treatment. Blood work, history, and scalp analysis are often more useful than experimenting with kitchen ingredients, he says.

Moronfolu says people are often better off concentrating on basic hair care practices that improve moisture retention and reduce breakage, especially for textured hair. Good technique, protective styling, and proper product use may do more for length retention than viral hacks.

And while many people turn to oils, Gaunitz says leaving oils on the scalp for long periods can sometimes do more harm than good by feeding microbial overgrowth. If oils are used, he recommends limiting how long they stay on the scalp and washing them out thoroughly rather than treating them as an all-day or everyday fix.

Echeverry also pushes back on the idea that “natural” automatically means safe. Produce can contain pesticide residues, she says, and applying untested food-based substances to an already compromised scalp barrier may create new problems rather than solving the original one.

The Takeaway

• Onion water has deep roots in traditional hair care practices, including Ayurvedic medicine and family traditions passed down through generations.
• While some people claim that onion treatments can reduce dandruff and hair loss and improve shine, the research evidence supporting their widespread use for scalp and hair conditions is minimal.
• If you want to try onion water or juice, squeeze chopped onions to extract the juice, then apply it to your scalp with a cotton pad before massaging it in.
• Although the theoretical risk and cost are low, consult a dermatologist or trichologist before attempting a DIY treatment. DIY approaches may not address all hair concerns, and you’ll likely need other, evidence-based treatments to manage conditions such as androgenetic alopecia.