Ampicillin skin reactions with

The incidence of nonallergic ampicillin eruptions is 40 to 100% in patients with concomitant Epstein-Barr virus (mononucleosis), cytomegalovirus, acute lymphocytic leukemia, lymphoma, or reticulosarcoma. Nonallergic penicillin-associated rashes are characteristically morbilliform (symmetrical, erythematous, confluent, maculopapular) eruptions on the extremities. The onset of typical nonallergic eruptions is more than 72 hours after (3-lactam exposure. The mechanism for the nonurticarial ampicillin rash is not known and is not related to IgE or type I hypersensitivity. Penicillin skin tests are not useful in the evaluation of nonurticarial ampicillin rashes. Patients with a history of nonurticarial ampicillin rashes may receive other (3-lactam antibiotics without greater risk of subsequent serious allergic reactions. 

Concomitant administration of allopurinol with ampicillin may increase the incidence of adverse skin reactions. In one study, these occurred in 22% of patients taking the combination (26). However, this interaction was not confirmed in a later investigation (27). 

A 40-year-old male nurse developed facial angioedema, dyspnea, rhinoconjunctivitis, dysphonia, and dysphagia immediately after opening a sachet containing amoxicillin and clavulanic acid (149). Skin prick tests were positive for both amoxicillin and ampicillin, and an open test with amoxicillin resulted in a severe immediate-type reaction with large localized wheals and erythema at 10 minutes. Six months later, when he was asymptomatic, erythema was observed during open tests with ampicillin 5%. 

The question of tolerability of penicillins, monobactams, and carbapenems in patients with IgE hypersensitivity to cephalosporins was recently assessed in 98 subjects by serum IgE antibody assays, challenge tests, and skin testing with penicillin reagents, aztreonam, imipenem-cilastatin, and meropenem. Approximately 25 % of cephalosporin-allergic subjects were positive to penicillins, while 3.1,2, and 1 % showed positive results to aztreonam, imipenem, and meropenem, respectively. A reaction to a cephalosporin with a similar or identical side chain to penicillin was a sigifificant predictor of cross-reactivity. For skin testing, the following concentrations were used ampicillin and amoxicillin 1 and 20 mg/ml cephalosporins 2 mg/ml aztreonam 2 mg/ml imipenem-cilastatin 0.5 mg/ml and meropenem 1 mg/ml. 

Jankowska, H. (1975) Skin reactions in response to ampicillin treatment in children with infectious mononucleosis (Polish). Pediat. Pol, 50, 1357. 

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