Legacy AI grade · Sources dated 2026-06-01. Not expert reviewed. Coverage is limited to the listed sources. About the new summary workflow
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