Allergic disorders commonly occur in patients with systemic lupus erythematosus (SLE) and allergies to some drugs may occasionally be related to disease flares. We evaluated the prevalence of several types of allergy in 132 patients with SLE and their families and compared the SLE patients with a control group of 66 patients with non-lupus disorders. Total IgE levels were tested in 117 SLE patients and 61 controls. Eighty-three of the 132 SLE patients (63%) had a history of at least one type of allergic disorder. This prevalence was significantly higher (P < 0.0001) than that of the control group (20 of 66 controls). The prevalence of drug allergy (38% vs. 17%; P < 0.005), skin allergy (36% vs. 17%; P < 0.01) and insect allergy (14% vs. 2%; P < 0.02) were significantly higher in SLE patients when compared with controls. Family members of SLE patients had an increased prevalence of at least one type of allergy (55% vs. 24%; P < 0.0001), allergic rhinitis (30% vs. 14%; P < 0.02), asthma (25% vs. 9% P < 0.02), and both rhinitis or asthma (44% vs. 20%; P < or = 0.002). The presence of allergy both in the patient and in the family was more frequent in SLE patients than controls (42% vs. 15%; P < 0.001). We found no differences in total IgE levels between the two groups. Drug, skin and insect allergies were particularly frequent in SLE patients. We also found a high prevalence of rhinitis and asthma in their families.