Definition
The primary furocoumarins responsible are bergapten (5-methoxypsoralen), oxypeucedanin, and psoralen. When these penetrate the skin and are then activated by UVA light, they produce a phototoxic reaction: immediate redness, followed by lasting hyperpigmentation (brown patches) persisting for months. This is not an allergic reaction but a direct chemical interaction with UV photons (Wikipedia EN, accessed 2026-05-27).
IFRA limits bergapten to 1 ppm in leave-on skin products, driving industry adoption of FCF citrus oils produced by vacuum distillation or molecular filtration. Affected materials include cold-pressed bergamot (the most problematic), lime, lemon, bitter orange peel, grapefruit, rue, and angelica root. Several classics including Eau Sauvage by Dior (1966) were reformulated because of these restrictions (IFRA, accessed 2026-05-27).
Niche context
Some niche houses revendicate natural, non-FCF bergamot as a quality statement, explicitly disclosing the photosensitizing risk. This tension illustrates a structural challenge for artisanal perfumery:
- Non-FCF Calabrian bergamot has a rounder, more complex aroma than its FCF counterpart.
- IFRA compliance is required for EU and US market access.
- Some boutique houses offer a compliant retail version alongside a non-FCF bespoke version sold with express photosensitizing warnings for professional use.