Pseudolymphoma (cutaneous lymphoid hyperplasia) is a benign inflammatory response that histologically and often clinically mimics cutaneous lymphoma. Both T-cell and B-cell forms of pseudolymphoma may be seen. Pseudolymphoma is characterized by dense lymphoid infiltrates of the skin, which may be focal or diffuse.

Triggers include insect bites or stings, which cause local reactions, or anticonvulsant drugs, which can cause widespread eruptions. Other causes include a broad range of non-anticonvulsant drugs (antihypertensives, lipid lowering agents, and antidepressants, among others), tattoo dyes, trauma, vaccinations, contact dermatitis, folliculitis, and infections (such as varicella, molluscum contagiosum, human immunodeficiency virus [HIV], or Lyme disease). Pseudolymphoma may be seen after scabies infection, particularly in children. Medication-related reactions may include fever, lymphadenopathy, and an erythematous skin eruption. Malaise, arthralgia, hepatosplenomegaly, eosinophilia, and abnormal liver function tests can also be present in medication-related cases.

While pseudolymphoma may occur at any age, it is most commonly seen in early adulthood.