Bergamot essential oil painful erythema and bullae on exposed areas of the skin. In one case, six (6) drops of bergamot aromatherapy oil in a bath followed by 20–30 minutes exposure of ultraviolet light from a tanning bed caused a severe burn-like reaction. Bergamot essential oil contains a significant amount of bergapten, a phototoxic substance that gets its name from the bergamot orange. Bergapten, a linear furanocoumarin derived from psoralen, is often found in plants associated with phytophotodermatitis. Note that bergamot essential oil has a higher concentration of bergapten (3000–3600 mg/kg) than any other citrus-based essential oil. When bergamot essential oil is applied
Bergamot orange skin of guinea pigs was shown to have a concentration-dependent phototoxic effect of increasing redness after exposure to ultraviolet light (due to the chemical bergapten, and possibly also citropten, bergamottin, geranial, and neral). This is a property shared by many other citrus fruits. Bergapten has also been implicated as a potassium channel blocker; in one case study, a patient who consumed four litres of Earl Grey tea per day (which contains bergamot essential oil as a flavouring) suffered muscle cramps. Bergamot is also a source of bergamottin which, along with the chemically related compound 6',7'-dihydroxybergamottin, is believed to be responsible