The action spectrum for induction of chronic actinic dermatitis is similar to that for sunburn inflammation.

The action spectrum for induction of the abnormal cutaneous response at 24 h in the photosensitivity disorder chronic actinic dermatitis (CAD) was determined in 15 patients and found to be the same in shape as that for normal sunburn in fair-skinned individuals at 24 h, as determined for 47 control volunteers, although displaced in magnitude. This suggests that an endogenous chromophore(s), the same as or similar to that/those responsible for human sunburn, may be responsible for initiation of the abnormal reaction to irradiation in CAD, and that the putative antigen associated with the CAD reaction may be derived from that/those or associated molecules.