Flare up to betalactams.

BACKGROUND: The flare up phenomenon has most frequently been described with nickel. Not many cases of flare up to drugs have reported in the literature, however we have reported it with different medications. METHODS AND RESULTS: A 31-year-old woman developed an adverse reaction with an antibiotic during her childhood. Prick test with penicillin (100,000 IU/ml), penicilloyl polylysine (PPL), minor determinant mixture (MDM), amoxicillin (200 mg/ml), ampicillin (200 mg/ml) and cephalotin (200 mg/ml), and intradermal test to the same substances diluted in saline were all negative immediately. We performed an oral challenge test with 500 mg of amoxicillin. Twelve hours later, the intradermal test to PPL and MDM became positive (PPL 10 x 10 mm, MDM 8 x 7 mm). All patch tests were positive after 72 hours with erythema, vesicles and infiltration and the patient also had exanthema with pruritus on her entire body. CONCLUSIONS: We present one patient with delayed allergic reaction caused by amoxicillin and penicillin, that we all know as Flare up. We suggest that this phenomenon of Flare up occurs by a Type IV mechanism mediated by T-cells without participation of IgE antibodies. The betalactam hypersensitivity mechanism which has usually been described is an IgE mediated reaction, but there are other not very well known mechanisms that are responsible for the delayed reactions.