Uncontrolled exposure to UV-A light following exposure to psoralens or other furocoumarins can result in a extensive damage to the epidermis resembling a second degree burn.


Furocoumarins are tricyclic compounds that can absorb UV-A light (320 to 400 nm). Psoralens are furocoumarin compounds used to treat vitiligo, psoriasis and a variety of other dermatologic conditions.


Furocoumarins occur naturally in many plants, including:

(1) celery

(2) figs

(3) caraway

(4) lemon


The burn is a partial-thickness burn like lesion resembling a second degree burn but sparing the dermis:

(1) erythema

(2) blistering

(3) diffuse epidermal necrosis with skin loss


A phototoxic reaction following exposure to sunlight and a plant containing a furocoumarin is called phytophotodermatitis (phyto = plant).


Severe reactions tend to occur when there is:

(1) diffuse exposure to a psoralen compound

(2) uncontrolled exposure to UV-A light, which can pass through regular glass



(1) Persons who handle psoralens or furocoumarins should wear gloves and protective clothing.

(2) Avoidance of suntan products containing psoralens or furocoumarins.

(3) Patients taking psoralens for a skin condition should have carefully controlled exposure to sunlight or UV-A light.


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