Onion Juice (Allium cepa) for Alopecia Areata
Topical onion juice has not been shown to reliably treat alopecia areata. The only positive human trial is a single small, low-quality study that has not been reproduced in over twenty years, and no health authority or dermatology body endorses it.
Why this grade7-layer evidence engine
The entire positive signal rests on one open-label randomized trial from 2002 (PMID 12196747, n=38, 6 weeks), which reported terminal hair regrowth in about 74% of evaluable onion-juice patients versus 13% with a tap-water control (P<0.0001). Although that gap looks dramatic, the trial was not blinded, described no allocation concealment, was very small, and ran only six weeks.
Two systematic reviews (PMID 30815439, 2018; PMID 12126069, 2002) both conclude this remains the sole RCT, with no independent replication and a high risk of bias. They emphasize that patchy alopecia areata spontaneously regrows in up to half of cases within a year and carries a 10-30% placebo response, which can account for much of the apparent benefit.
Regulators and clinicians do not back this use: the FDA lists onion only as a GRAS food ingredient (safety, not efficacy), the WHO records only traditional oral uses with no hair-related claim, and NIH ODS, Mayo Clinic, Cleveland Clinic, Harvard Health, and the relevant dermatology society are all silent on it. A plausible mechanism plus one small unreplicated trial and no professional endorsement is exactly why this grades as weak, disputed evidence rather than effective.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.568
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 無高階證據可裁決
- tier_strict_requirement_check — | B→C 因 scope.conflation_risk=true 且 L11 獨評較低 (B7-2 tier cap)
- detect_disputes — 偵測到 1 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status