Definition
Furanocoumarins cause their sensitizing effect by intercalating into DNA under UV radiation, producing a phototoxic reaction (immediate redness and burning) or a photoallergic reaction (delayed hypersensitivity). The clinical phenomenon, called berloque dermatitis, was historically common among users of citrus-heavy colognes who wore them outdoors in summer.
Bergapten-free bergamot oil retains the olfactive character of the original while removing the sensitizing component, making it the standard for most contemporary perfumery applications.
Regulation and practice
Bergapten (5-methoxypsoralen) is the primary furanocoumarin of concern in bergamot essential oil, present at 0.3-0.5% in cold-pressed Calabrian bergamot. Under IFRA's 50th Amendment, bergapten-rich bergamot is restricted to very low levels in leave-on products applied to sun-exposed areas; most commercial perfumers use bergapten-free bergamot (FCF: furanocoumarin-free, achieved by vacuum distillation or solvent extraction) for skin-safe formulas (IFRA, accessed 2026-05-27).
Other furanocoumarin-rich materials: cold-pressed lemon oil, lime oil, grapefruit oil, and angelica root oil. All require attention in leave-on, sun-exposed applications. The practical effect: many classic colognes and fresh-citrus niche fragrances now specify FCF citrus oils or use synthetic citrus molecules without photosensitizing components (Fragrantica encyclopedia, ECHA, accessed 2026-05-27).