Amoxicillin is a useful and commonly used antibiotic.  Sometimes, kids who take it develop a rash.  Parents wonder: could this be a reaction or an allergy?  Must the drug be stopped?  Should I run to the ER?

Of course, to be certain about a drug reaction, the child should be examined.  However, if the child seems otherwise well (no fever, acting ok etc.), you can wait until regular office hours.

The most common reaction to amoxicillin is a red bumpy rash.  We call it an “amoxicillin reaction” or an “Amoxil reaction” (named for the original “brand” of amoxicillin).  Do you see little red raised bumps, like mosquito bites, all over the trunk or limbs?  It may look very dramatic, but it probably doesn’t itch or bother the child.  It usually starts about 5-7 days after the amoxicillin was begun; it fades after a few days with no treatment, even if the amoxicillin is continued.

This “Amoxil reaction” is not dangerous, and is not an allergy.  It is also not a reason to avoid amoxicillin in the future.  We think that it may be an interaction between the amoxicillin and another virus temporarily in the child’s immune system.

Of course, any child might develop a true allergy to amoxicillin (or any drug) that might require stopping the drug or giving further treatment.  If you see coin-sized (or bigger) blotches, especially if they’re itchy, this is of more concern.  If there is any question, give us a call or schedule an appointment.  And of course, if the child is wheezing or otherwise especially ill, call right away!

–  David M. Epstein, MD