erythema multiforme

My son developed EM while on an antibiotic as an infant.  It never progressed to Stevens-Johnson syndrome but was pretty severe.  Over the years he used alternative antibiotics for ear infections etc.  He was tested by an allergist and was found not to be allergic to the medication he was on during that time period.  So what caused the EM?  Is it likely to happen again.  It was very scarey.  His eyes swelled shut and he had these "bullseyes"  popping up all over his body.

[National Jewish Health]

If there was a temporal relationship between the antibiotic administration during infancy and the development of Erythema Multiforme (EM), it is highly likely that the EM was caused by the antibiotic.  In that case, your son should never be given that antibiotic or any medicine in its class, again.  If it happens to be a one-of-a-kind antibiotic for which there is no good substitute, one he could conceivably need in the future, you would do well to consult with an infectious disease specialist now, rather than waiting until such time, as the need for it is great.  The allergist's observation and conclusion may be correct but you should not put your son at risk of having another severe reaction, on the basis of one negative allergy test.

[sue3708]

He has been on the antibiotic after skin testing and an oral challenge probably 3-4 times now since the oral challenge....  should we still withold that antibiotic or consider it safe since there have been no problems  on it at this point?