Sunburn

Characteristic history and physical examination findings are usually sufficient to make the diagnosis of sunburn. Biopsy is rarely indicated or necessary.

History

History reveals recent prolonged sun exposure. Signs and symptoms of sunburn may begin 2 to 4 hours after severe ultraviolet (UV) over-exposure. Erythema peaks by 12 to 24 hours, but pain, discomfort, and other symptoms may have a longer time course. In more severe cases, systemic symptoms, including nausea, chills, and malaise, should be investigated. In order to screen for risk factors, physicians should enquire about outside activity during peak sun hours, use of sunscreen and/or protective clothing, and, if relevant, the type of sunscreen used. Both topical and systemic medications should be reviewed to evaluate for potential photo-sensitising, photo-toxic, or photo-allergic reactions.

Physical examination

Physical examination may demonstrate erythema, oedema, vesicles/bullae, and desquamation, often accompanied by increased warmth and tenderness of the skin. Photo-distributed freckling and lentigos, with or without diffuse scaly erythematous actinic keratoses, indicate chronic actinic damage due to repeated over-exposure to UV radiation and a higher risk for developing photo-ageing and skin cancer. In more severe cases of acute sunburn, vital signs should be assessed to monitor haemodynamic instability and hydration status. Total body surface area involvement should be estimated (e.g., the palm of the hand, including fingers, equals 1%). For the purposes of evaluating potential hospitalisation only the blistered surface area should be measured. Those with evidence of repeated UV over-exposure should be subject to total skin examination for malignant melanoma and other forms of skin cancer.

Investigations

Skin biopsy is rarely necessary and should only be performed to rule out other entities in the differential diagnosis. A skin biopsy would show scattered eosinophilic keratinocytes with absent or pyknotic nuclei (apoptotic "sunburn cells") in suprabasal and mid-epidermal layers.[15]Van Laethem A, Claerhout S, Garmyn M, et al. The sunburn cell: regulation of death and survival of the keratinocyte. Int J Biochem Cell Biol. 2005;37:1547-1553. http://www.ncbi.nlm.nih.gov/pubmed/15896663?tool=bestpractice.com Phototesting is rarely indicated, only when diagnosis is in doubt. It involves assessment of the minimal erythemal doses for ultraviolet A and ultraviolet B to detect abnormal photosensitivity.