Penicillin allergy occurs in approximately 1-10%. However life-threatening problems are rare - anaphylaxis (bad reaction requiring other treatment) occurs in about 15-40/100,000. Death in about 1.5-2/100,000.
I have been allergic to pencillian since i was 18 (over use as a child) ie: neurotic mother shovelling down shit loads of medication to us kids cos we either had a snotty nose or the odd spot ... its been a pain at times, because certain infections can be cured by the simplist penicillian, were'as like me, ive often had to have a combination of pills ...just to do the trick! heaven forbid getting a dose of the clap! (penicillians dream) id be buggered (litterally) JJ
Erythromycin is commonly prescribed for those allergic to penicillin. I understand that an actual allergic reaction to erythromycin is actually very uncommon although a bad reaction and side effects of nausea and vomiting are fairly widespread. For those affected, clarithromycin is suitable. It was developed to overcome the side effects of erythromycin but is otherwise similar in function.