Polymorphic light eruption (PLE) is approximately four times more common in women than in men and often begins in young adult life. It is hypothesized that patients with PLE have an inherent resistance to UVL-induced immunosuppression, which is a physiological phenomenon in normal healthy individuals. Consequently, in PLE there is a delayed-type hypersensitivity reaction to a UVL-modified skin antigen, which results in an inflammatory reaction and a variable rash. The female hormone, 17β-oestradiol, has been shown to inhibit UVL-induced physiological suppression of contact hypersensitivity responses. This has been postulated to account for the female preponderance of PLE. If 17β-oestradiol plays a significant part in the disease, one might hypothesize that the severity of PLE might reduce in women after menopause.