Author: Dr Ian Coulson, Consultant Dermatologist and Editor-in-Chief, 2023.
Edited by the DermNet content department
This 35-year-old woman has had three episodes of redness and blistering affecting the same area on only one foot in the last four years.
Her only other medical problem is recurrent urinary tract infections.
The recurrent development of redness and blistering in exactly the same place on the skin is very suggestive of a fixed eruption, most commonly caused by drugs. Occasionally they can be caused by foodstuffs, preservatives and other food and beverage additives. Lesions may be solitary or multiple. Uncommon sites to develop fixed eruptions are the lids, lips, palms, soles, and genitalia.
They frequently arise within minutes or hours after exposure to the offending agent, once sensitisation has occurred. When they resolve, they commonly leave areas of hyperpigmentation.
The likely cause in this case is the antibiotic used to treat her urinary tract infections.
Avoiding the offending drug, and similar potentially cross reacting drugs, is the most important aspect of treatment. If there is a blister, then this can be aspirated leaving the roof intact as a biological dressing. A potent topical steroid can then be applied until the inflammation resolves.
