Encyclopedia · botanical
Onion juice
A 2002 Iraqi study found crude onion juice regrew hair in patchy alopecia areata, but the control was tap water, the groups were small, and it was not shown for pattern hair loss.
What it is
Onion juice is crude juice squeezed from the bulb of Allium cepa, applied to the scalp and usually rinsed off. Onion extract is also sold in shampoos.
How it works
The mechanism is not established. Hypotheses include an irritant or allergic response that changes local immune activity (the idea behind "contact immunotherapy" for alopecia areata), sulfur compounds and antioxidants. None has been tested here.
What the studies show
- In 38 people with patchy alopecia areata, crude onion juice twice daily for 2 months (23 people) versus tap water (15 people) gave regrowth in 73.9% at 4 weeks and 86.9% at 6 weeks, versus 13% at 8 weeks with water. Sharquie 2002
- A systematic review of 16 studies of complementary treatments for alopecia areata found essential-oil aromatherapy, topical garlic and peony glucosides had the best evidence, with rare and mild adverse events and limited quality. Tkachenko 2019
- A 2025 review lists onion juice among promising but weakly evidenced remedies. Ahmed 2025
Weaknesses: the abstract does not describe randomization or blinding, which would be hard given onion's smell; alopecia areata often regrows by itself; there was no sample-size justification and no replication. The study says nothing about pattern hair loss.
How it's used in studies
Crude juice applied to patches twice daily for two months.
Side effects and safety
Expect a strong smell, stinging and redness. Allergic contact dermatitis to onion and garlic is documented (Cantisani 2014). Do a patch test, stop if the scalp blisters, and avoid the eyes.
Bottom line
Limited evidence for patchy alopecia areata, and weak even there; it is not recommended for pattern loss. Alopecia areata deserves a dermatologist (see alopecia areata), and onion juice is a smelly, low-evidence extra. Discuss with a doctor.
Studies 4
Sharquie KE, Al-Obaidi HK. Onion juice (Allium cepa L.), a new topical treatment for alopecia areata. J Dermatol. 2002
Tested: crude onion juice twice daily (23 people) vs tap water (15 people)
Result: Regrowth in 73.9% at 4 weeks and 86.9% at 6 weeks with onion juice vs 13% at 8 weeks with tap water.
Read the study ↗Tkachenko E et al. Complementary and alternative medicine for alopecia areata: a systematic review. J Am Acad Dermatol. 2023
Tested: complementary and alternative treatments
Result: Essential-oil aromatherapy, topical garlic and peony glucosides had the best evidence; adverse events were rare and mild; quality was limited.
Read the study ↗Ahmed A et al. Herbal remedies for hair loss: a review of efficacy and safety. Skin Appendage Disord. 2025
Tested: herbal hair-loss remedies including amla and onion juice
Result: Names amla and onion juice among remedies backed by small, short studies.
Read the study ↗Cantisani C et al. Unusual food allergy: Alioidea allergic reactions overview. Recent Pat Inflamm Allergy Drug Discov. 2014
Tested: Allium exposure
Result: Documents allergic reactions to onion and garlic.
Read the study ↗Related
- GarlicA 2007 Iranian trial found garlic gel added to a steroid cream improved patchy alopecia areata, but raw garlic is a known skin allergen and nothing supports it for pattern hair loss.
- Rosemary oilRosemary oil became the internet's "natural minoxidil" from one small 2015 trial that had no placebo group and has never been replicated.
- Black seed oilBlack seed oil's hair reputation rests on animal work and a tiny open-label lotion study, with no independent controlled human trial.
- Alopecia areataAn autoimmune condition where the immune system attacks growing hair follicles, causing round patches or total hair loss; three oral JAK inhibitors are approved for severe cases but hair usually goes again when treatment stops.