Polymorphous Light Eruption - Western SummaryWestern Medicine Summary

Western Medicine

Western Summary

Polymorphic light eruption (PMLE) is a photosensitivity reaction to sunlight and ultraviolet light. This can have many different appearances on the skin with one common finding that it occurs in areas of light exposure, most often the face, neck, chest and arms. 

Symptoms

One of the more classic appearances is that of red bumps. Sometimes small blisters may occur or the rash may mimic lesions of eczema.[1] Women tend to be affected more commonly than men.[2] Although PMLE is triggered by sunlight, the lesions tend to improve with continued exposure through a mechanism known as “hardening” where the skin becomes more and more tolerant to sun exposure. For example, the rash may improve over the course of the spring and summer. The same pattern may occur every year with worsened rash at the beginning of the spring and summer months and improvement over the course of the sunny season.  

Causes

The exact cause of PMLE is not known though it appears to be a type of sensitivity reaction to both UV light (types A and B) as well as the visible light spectrum.[1,2] PMLE often occurs when sun exposure increases in a short period of time, such as season changes in the spring and summer. 

Treatments

Sun protection and avoiding prolonged periods of sun exposure are critical. 

  • Steroids: Topical steroids have an anti-inflammatory effect. 
  • Antihistamines: Antihistamines help control itching.
  • Intentional UV exposure: It may seem counterintuitive but treatment with UV light therapy administered in a medical office in measured doses can help decrease the occurrence and symptoms of PMLE by inducing “hardening” where the skin becomes more tolerant to light exposure. 

1.    Boonstra HE, van Weelden H, Toonstra J, et al. Polymorphous light eruption: A clinical, photobiologic, and follow-up study of 110 patients. J Am Acad Dermatol.2000;42(2 Pt 1):199-207; PMID: 10642673.

2.    Gruber-Wackernagel A, Byrne SN, Wolf P. Polymorphous light eruption: clinic aspects and pathogenesis. Dermatol Clin.2014;32(3):315-334, viii; PMID: 24891054.