Hair loss is a common dermatological concern that can arise from several factors, including genetic predisposition, hormonal imbalances, nutritional deficiencies, inflammatory conditions, and autoimmune disorders. Among these, alopecia areata (AA) is an autoimmune condition characterised by sudden, patchy, non-scarring hair loss, primarily affecting the scalp but potentially involving any hair-bearing area of the body.
Although several therapeutic approaches are available for managing AA, interest in natural remedies has increased, particularly in the use of onion (Allium cepa) juice as a topical hair-growth intervention. Traditionally recognised for its medicinal properties, onion has attracted scientific attention because of its sulphur-containing compounds and antioxidant constituents.
Bioactive constituents and potential mechanisms of action1
The potential hair-growth-promoting effects of onion juice have primarily been attributed to its sulphur-containing compounds and phenolic constituents.
- Sulphur is an essential component of amino acids, including cysteine, which contributes to the formation of keratin, the structural protein responsible for hair strength and integrity. Its antimicrobial and potential anti-inflammatory properties may also contribute to a healthier scalp environment.
- Additionally, onion juice contains antioxidant compounds, particularly flavonoids such as quercetin. These constituents may help mitigate oxidative stress and inflammatory processes through their antioxidant activity. As oxidative stress and immune-mediated inflammation are implicated in the pathophysiology of AA, these properties have been proposed as potential contributors to hair regrowth.
- However, the precise mechanism through which onion juice promotes hair regrowth in AA has not been established. One proposed explanation involves the induction of mild irritant contact dermatitis by sulphur-containing and phenolic compounds. This local inflammatory response may potentially stimulate hair regrowth through a process described as antigenic competition, although this hypothesis remains insufficiently validated.
Clinical evidence: Does onion juice promote hair regrowth?
The hair-growth-promoting potential of topical onion juice in individuals with patchy AA has been explored in clinical research, with promising outcomes reported.
- In a comparative clinical study, the efficacy of crude onion juice was evaluated against tap water over an 8-week treatment period.
- Noticeable regrowth of terminal hairs was observed as early as two weeks following the initiation of onion juice application, with response rates increasing progressively over the treatment period.
- By the 6th week, hair regrowth was demonstrated in approximately 87% of participants receiving onion juice, whereas only 13% of those in the control group exhibited regrowth after 8 weeks. A significantly greater improvement was observed with onion juice than with tap water.2
Safety considerations and limitations
Despite the encouraging findings, certain limitations and tolerability concerns should be considered before onion juice is regarded as a therapeutic intervention for hair loss.
- An unpleasant odour was identified as a major drawback of topical application, potentially affecting treatment acceptability and adherence.
- Additionally, local irritation and irritant contact dermatitis may occur following exposure to onion juice.
- Although mild inflammation has been proposed as a possible contributor to hair regrowth, excessive irritation may cause discomfort and aggravate scalp inflammation.
Conclusion
Onion juice (Allium cepa) has demonstrated preliminary potential as a topical intervention for promoting hair regrowth in individuals with patchy AA. Its sulphur-containing compounds and antioxidant constituents, particularly quercetin, have been proposed to contribute to its potential therapeutic effects through antioxidant, antimicrobial and immunomodulatory activities. The encouraging outcomes reported in an early clinical study warrant further investigation.1,2
References:
- Ahmed A, Alali AM, Abdullah E, et al. Herbal Remedies for Hair Loss: A Review of Efficacy and Safety. Skin Appendage Disord. 2025;11(4):360-371. doi:10.1159/000542876 https://pmc.ncbi.nlm.nih.gov/articles/PMC12324729/#s3
- Sharquie KE, Al-Obaidi HK. Onion juice (Allium cepa L.), a new topical treatment for alopecia areata. J Dermatol. 2002;29(6):343-346. doi:10.1111/j.1346-8138.2002.tb00277.x https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1346-8138.2002.tb00277.x?sid=nlm%3Apubmed