Cardi B Washes Her Hair with Onion Water—Here's Why

From her makeup to her manis, Cardi B's beauty looks have been turning heads since she burst onto the scene. But lately, it’s her long, luscious locks that have captured our attention. Turns out the secret to her mane isn’t the magic touch of a celebrity hairstylist or an exclusive product—it’s onion water. The Grammy-winning rapper shared that she uses it to wash her strands. "My last two washes I been boiling onions and using the water to wash my hair," she posted on Instagram. "I used to do this six years ago when I started my healthy hair growth journey. I stopped cause I got really lazy. It's odorless, and I notice that it’s been giving a shine to my hair."

Her Instagram post features a picture of her long locks after she started this DIY treatment—and the results are impressive. We’re talking high wattage shine and strong, long locks that look incredibly healthy. To learn more about the hair benefits of onion water, we spoke with experts to learn why Cardi B uses it (and if you should, too).

What Is Onion Water?

Though you might pass on onions in your salad, onion water for hair is a different story. "Onions are finally getting recognition and are no longer an industry secret as the go-to beauty ingredient," says Kerry E. Yates, trichologist and founder of Colour Collective, a beauty brand development agency.
Rich in antioxidants and flavonoids, onions are anti-microbial, anti-fungal, and anti-inflammatory; they are perfect problem-solvers for hair challenges like dandruff."

In other words, Cardi B is onto something. "Onion water has gotten some press and social media attention as being good for hair growth and health," adds Dr. Jodi LoGerfo, DNP, APRN, FNP-BC, DCNP, a dermatologist at Orentreich Medical Group in New York City. 

Benefits of Onion Water for Hair

Onion water is loaded with good-for-you nutrients. However, it's important to note that the use of onion water for hair has not been studied much. "There was a small study published in the Journal of Dermatology that tested onion juice as a treatment for alopecia areata (a type of autoimmune hair loss)," Dr. LoGerfo says. "The study concluded that onion juice was effective in inducing hair growth, but the mechanism by which it worked was not clear. The downside was that the study contained a very small number of participants."

Despite the lack of studies—and hence no concrete evidence that onion water is good for hair—it's still worth a shot. "I'm not against trying it," Dr. LoGerfo says. "The anecdotal information seems to be positive." These are the perks of onion water for hair:

Boosts shine: "It enhances shine and overall hair beauty," Yates says.

It's loaded with sulfurous compounds: "The theory on using onion water for hair is based on onions containing many nutrients including sulfur, which is considered an important mineral for hair growth and keratin production (one of the components of hair)," Dr. LoGerfo says. "Sulfur may also improve hair growth." Additionally, sulfur can help strengthen hair and improve elasticity.

Helps manage scalp health: Onions' anti-inflammatory and antifungal properties may help improve scalp irritation and itch. "It can alleviate fungal infections that can cause dandruff," Yates says. "It also aids in improving circulation when combined with a scalp massage." 

Delivers nourishing vitamins to the follicles: "Vitamin A is an all-around good vitamin that helps keep the scalp healthy; it establishes an optimal environment to ensure hair growth and overall beauty," Yates says. "Onion water also has vitamin C, a powerful antioxidant that protects the hair and scalp from environmental challenges."

It's rich in quercetin: "A natural antioxidant, anti-inflammatory, and anti-bacterial, various studies have found quercetin can inhibit PGD2, which negatively impacts the hair life cycle," Yates says. Quercetin is a type of flavonoid that onions are packed with. "Flavonoids can protect the skin from free radical damage and aging, which can improve the health of the hair follicle," Dr. LoGerfo says. "These flavonoids can also have vasodilatory properties, which increase the blood flow to the scalp (and to the follicle), which may increase hair growth. 

Hair Type Consideration

Since there haven't been in-depth studies on onion water for hair, it's unknown what hair types it's best for and if any should avoid it. However, Dr. LoGerfo says it is likely suitable for all hair types.

Those with an onion allergy should steer clear of the DIY treatment. "Onion juice and onion water can induce an allergic contact dermatitis (skin allergy) in those who are allergic or sensitive," cautions Dr. LoGerfo.

How to Use Onion Water for Hair

"Making onion water or juice entails peeling and chopping onions and placing them in a juicer to squeeze out the juice or putting it into a blender and making a paste," Dr. LoGerfo says. "Once it is a paste, you can put it on a strainer or cheesecloth to squeeze the juice (or extract) out. You could also chop the onions and soak them overnight in water. Then apply the onion-infused water in the morning."

According to Yates, when used as an onion water rinse, it's best not to use it more than once a week. "Some people will dab onion juice directly onto the scalp every other day," she says. "The challenge, however, can be the smell. The negative fragrance from onion can be offset with lemon juice. However, it is wise to find a topical treatment containing onion juice and/or an ingestible to help secure gorgeous hair and a healthy scalp."