Author: Dr Ian Coulson, Consultant Dermatologist and Editor-in-Chief (2025).
Edited by the DermNet content department.
This 45-year-old lady has recurrent urinary tract infections; every time she gets one, she develops an inflamed lesion in the same place on her left sole. On the last occasion, she developed a blister.
Urinary tract infections are treated with antibiotics, such as trimethoprim. The reliable development of inflammation in the same site is highly suggestive of a fixed drug eruption. Often there is oedema and inflammation, but sometimes the inflammation is profound enough to produce blistering.
The antibiotic is the likely cause of this problem. Many drugs can cause fixed drug eruption, but antibiotics are the most commonly implicated.
A clue to fixed drug eruption is that, as the inflammation subsides, there is often prolonged hyperpigmentation of the affected skin.
