Is Onion Water the Secret to Hair Growth? Here's What Science Says

There are a lot of strange things that end up on our hair in an effort to get stronger strands, healthier scalps, and shiny finishes. Maybe you’ve heard of apple cider rinses or even beer treatments, but what about onion water for hair? People claim that onion water can transform their strands, promoting hair growth and strength—but does this kitchen DIY live up to the hype? We consulted pros for answers.

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Benefits of Onion Water for Hair

You make onion water by soaking sliced, raw onion in a jar of water. The idea is that its juices—which are rich in sulfur, flavonoids, and antioxidants—seep into the water over time. The liquid is then applied directly to your scalp and strands. 

“Onion water is said to potentially improve the appearance of strength of hair by keeping scalp skin and hair follicles healthy and protected from oxidative stress,” explains Brendan Camp, MD, FAAD, a board-certified dermatologist at MDCS Dermatology in New York City. 

Candace Spann, MD, FAAD, a board-certified dermatologist in Las Vegas, notes additional claimed benefits for the scalp. “Sulfates in onion water can help to calm scalp dermatitis, soothe itchy scalp, and help encourage hair growth,” she says. 

The verdict’s still out on whether onion water for hair is going to deliver significant hair growth results, but there are studies that indicate it can promote hair growth by increasing blood flow. A 2002 review showed signs of hair regrowth in almost 87% of people with alopecia areata when applied twice a day. However, while a flavonoid in onions known as quercetin is thought to stimulate blood flow, it doesn’t affect hormones (including DHT), so it’s not a miracle solution for pattern baldness.

All that’s to say that the concept of onion water for hair is intriguing and has potential, but there’s just not enough information right now to say it’s the most effective approach to growing your hair (compared to FDA-approved routes like minoxidil). However, it’s worth a shot if you have interest in natural hair growth remedies.

Side Effects of Using Onion Water on Hair 

Any time you DIY a beauty recipe, you’re potentially putting your skin and hair at risk. Professionally formulated products include ingredients at optimal levels and preservatives to prevent the formation of harmful bacteria. 

“DIY products are usually made to be very concentrated and may result in adverse reactions that may include skin irritation, redness, itching, or a rash on the scalp,” says Nathan Newman, MD, FAAD, a board-certified dermatologist and cosmetic surgeon. 

And then there's the most obvious drawback: the stink. He adds that hair discoloration is another potential complication, especially those with light-colored hair, noting that frequent use of onion juice might cause a temporary yellowish tint in the hair.

Things to Consider Before Trying Onion Water for Hair Growth

If you like the idea of experimenting with onion water, Korab notes there are hair care products formulated with onion water, extract (allium cepa extract), or juice. These are combined with other ingredients that help nourish your strands, too, essentially “combining the benefits of onions with other components for a well-rounded formula to enhance hair health.” 

But if you’re currently struggling with hair loss and really want to get ahead of it, your best bet is products made with minoxidil or finasteride, which are backed by more scientific studies proving their efficacy.

"Minoxidil is the only FDA-approved ingredient to treat hair loss topically. Topical finasteride also has demonstrated benefits for some,” Dr. Spann says. Dr. Camp adds ketoconazole shampoo to this list, which can help target dandruff to promote a healthier scalp and therefore stronger, shinier, healthier strands. 

When struggling with ongoing hair loss or health, Dr. Newman suggests speaking with a doctor. “It is always best to consult with your dermatologist to evaluate the reasons for your hair loss," he says. "There are many causes for hair loss that can be medically treated including hormonal, auto-immune, and infectious induced hair loss.”