Fixed drug eruption (FDE) is a cutaneous adverse drug reaction that recurs at the same body site each time the individual is re-exposed to the culprit drug. One or more sharply demarcated, red or violaceous patches that are typically round develop within minutes to hours of exposure to the inciting drug. These may vary from 0.5 to several centimeters in size. They are usually asymptomatic, although burning, pain, or pruritus may occur. While any cutaneous surface may be affected, the oral and anogenital mucosa are most frequently involved.

FDE is most commonly solitary, but some individuals may develop multiple patches. There may be an increasing number of patches seen with each exposure. Healing with postinflammatory hyperpigmentation is common. Atypical variants include nonpigmenting and generalized blistering forms.

Numerous drugs have been implicated in causing FDE. The most commonly associated drug classes include antibiotics (in particular sulfonamides, trimethoprim, fluoroquinolones, and tetracyclines), NSAIDs (including naproxen, ibuprofen, and celecoxib), and barbiturates. Other specifically implicated drugs include amoxicillin, erythromycin, metronidazole, fluconazole, paracetamol (acetaminophen), cetirizine, hydroxyzine, methylphenidate, oral contraceptives, quinine, and phenolphthalein. Biologic agents including ustekinumab, adalimumab, and abatacept have been reported to cause fixed drug eruptions. A nonpigmenting variant is seen with pseudoephedrine.