Hydroxycitronellal

Hydroxycitronellal is a fragrance ingredient (synthetic floral odorant) used at low concentrations but is a well-documented contact allergen in patch-testing, including inclusion in fragrance allergen screening panels. Even at typical leave-on levels, it can trigger irritant and allergic contact dermatitis in sensitive individuals, with higher risk on compromised eczema-prone skin and with repeated exposure in multi-fragrance routines. Given its non-essential function and meaningful sensitization history, I score it as a significant irritancy risk. Safety Notes: Hydroxycitronellal is a fragrance ingredient used at trace levels in lightly fragranced leave-on skincare (often ~0.0001–0.01% when present as part of a parfum compound) and somewhat higher in fragranced rinse-off products where total perfume load can be higher. The upper end observed in consumer products is driven by strongly fragranced mass-market lotions/creams and some high-fragrance body products, where hydroxycitronellal can reach ~0.1–0.6% depending on the perfume composition. Use levels are practically constrained by IFRA allergen labeling considerations and sensitization risk, so very high percentages are uncommon outside fragrance-forward products.