Is This Onion Water Hack the Secret to Healthy Hair?

Cardi B recently set social media ablaze when she took to Instagram to share a potentially unexpected secret to healthy hair: onion water.

The rapper says that the DIY, at-home treatment has left her hair shinier after just two washes — and the supposed before-and-after pictures she posted to Instagram are undeniably convincing.

She may be the first female rapper to have three diamond single certifications from the Recording Industry Association of America, per Paper Magazine, but she’s certainly not the first to use the at-home hair treatment. Countless followers who flocked to Cardi B’s comments section praised the performer for utilizing the natural remedy, as it’s deeply embedded in ayurvedic practices and Dominican culture (though it’s unclear where the practice originated). And William Gaunitz, a certified trichologist, or hair and scalp expert, and founder of Advanced Trichology in Phoenix, Arizona, says that his hair loss patients have been discussing this natural treatment for years.

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.

While Cardi B’s hack involved boiling onions and using the water, Gaunitz notes that he’s encountered patients who’ve blended onions to make a juice-like substance that they use as a scalp treatment before rinsing it off in the shower.

Still others chop the vegetable and add it to their shampoo. That’s the case for PureWow writer Angie Martinez-Tejada, who learned about the supposed trick from her Dominican mother. She used the onion shampoo first and followed up with a second shampoo, which she says masks any lingering onion scent.

But what does the science say about this hair-raising hack? Ahead, we break down everything you need to know before you douse your hair in onion water.

What Are the Health Benefits of Onion Water for Hair?

Onions’ health properties mean the vegetable may offer a bevy of benefits for the hair. “Rich in antioxidants and flavonoids, onions offer antimicrobial, antifungal, and anti-inflammatory benefits,” says Kerry Yates, a trichologist and founder of Colour Collective based in Dallas. These properties make it a potential solution to alleviate fungal infections that can cause dandruff, she adds. While there’s a lack of high-quality research on how these properties translate to your scalp, one review published in 2020 in the Journal of Pharmacy and Bioallied Sciences noted the antifungal and antimicrobial potential of onion extract and onion essential oils.

And while research on the real-world applications of onions for hair is limited, one past study suggested that onion water could help promote hair re-growth among study participants living with alopecia areata, which is a condition that causes hair loss.

The study involved 38 women and men who applied onion juice or tap water to their scalp twice daily for two months. Of the 23 participants who used onion juice, 20 people (or 87 percent) noticed regrowth by six weeks into the trial, while only two people from the tap water group noticed the same. But the small sample size of this study means that further research is needed to fully understand this potential effect.

One possible reason onion juice may be a boon to your hair? “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, per past research. This nutrient leaves you teary after chopping onions, noted The New York Times. But it can have other effects, Gaunitz continues: “Since sulfur is a common OTC treatment for inflammatory skin conditions when applied to the scalp, it works for many people who have inflammatory hair loss issues.”

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, says Gaunitz. There’s no research to suggest that onion juice could suppress dihydrotestosterone levels to prevent androgenetic alopecia. Likewise, it hasn’t been shown to boost protein or vitamin D levels at the base of the hair follicle, which could assist in nutritional hair loss.

In either of those cases, it’s best to consult with a certified dermatologist or trichologist.

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