Onion extract (often from Allium cepa) is used topically for its flavonoid content, notably quercetin and cepalin, and is commonly included in scar-treatment formulations for its anti-inflammatory, antibacterial, and fibroblast-modulating properties. Evidence for visible scar improvement is mixed, with some studies showing benefits in scar texture and erythema and others showing minimal effect.
| Reported effect | How often | Notes |
|---|---|---|
Skin irritation or mild burning/stinging | Uncommon | Transient sensation at application site, more likely on broken or healing skin. |
Erythema (redness) | Uncommon | Localized and usually resolves after discontinuation. |
Allergic contact dermatitis | Rare | Hypersensitivity to Allium species; presents as itching, rash, or eczema. |
Contact urticaria | Very rare | Immediate hives in sensitized individuals. |
Frequencies reflect typical cosmetic use reported in the literature, not a guarantee for your skin.
Peer-reviewed papers on this ingredient, via PubMed.