Limited evidence and only for patchy alopecia areata — a small study showed regrowth there, but not for ordinary pattern baldness.
The buzz comes from a small 2002 study in which applying onion juice twice daily regrew hair in many people with alopecia areata (the autoimmune, patchy type), likely via sulphur compounds and irritation that nudge the immune response. Importantly, that's a different condition from androgenetic (pattern) hair loss, where onion juice has essentially no supporting evidence.
Bottom line: if you have patchy alopecia areata, onion juice is a cheap experiment with some (weak) support — but see a dermatologist, as far better treatments now exist. For pattern thinning, skip it: the smell, irritation and lack of evidence aren't worth it. Use proven treatments instead.
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FAQ
Does onion juice regrow pattern baldness?
There's no good evidence for that. The supporting study was in alopecia areata (the patchy autoimmune type), not androgenetic pattern loss, where onion juice isn't shown to work.
How is onion juice used for hair?
In the study it was applied to the scalp twice daily. Expect a strong smell and possible irritation. For alopecia areata, see a dermatologist about modern, far more effective options first.
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⚠️ When to see a doctor — don’t self-treat
- Sudden patchy or circular bald spots
- Redness, scaling, pus, pain or itch (possible scarring alopecia — treat urgently)
- Broken hairs or rapid loss
- Loss with body-wide signs (weight loss, fatigue, cycle changes, acne, extra hair)
- Loss right after a new medication
- Any hair loss in a child