Penicillin was the first antibiotic to be discovered and fortunately the best one ! It is extrremely safe and very cheap. It kills the most common bugs and is the most commonly prescribed antibiotic in the world.
Allergy to Penicillin is the most common drug allergy. It can be fatal as well. Penicillin or Penicllin derivateives (beta lactam antibiotics) like Ampicillin, Amoxicillin, Flucloxacillin and Co-amoxiclav (Augmentin) are prescribed for common infections like tonsillitis, ear infections, chest infections etc. Some children (and adults) develope a reaction after these drugs in form of a rash, swelling of face and sometimes breathing difficulties.
The most common reaction is a rash but most infections will give you a rash anyway. This leads to a misdiagnosis of Penicillin allergy in children who are actually not allergic. This creates a major problem as the alternatives to Penicillin are not great. They are expensive, not well tolerated and lead to development of resistance in organisms.
The diagnosis of Penicillin allergy is not easy. The blood test is very unreliable and the Skin Prick test is also not 100% sensitive or specific. The best (or best possible test) is called ‘Peniciliin Provocation test’. In this, the medicine (Penicillin) is given in increasing doses (while the child is well). We then watch for the development of a rash, in the next few hours to days. It could be an immediate reaction or a delayed reaction. It could be delayed for upto 5-7 days.
It is important to rule out Penicllin allergy specially if the child has a chronic condition like Cystic Fibrosis where they need multiple courses of antibiotics for recurrent infections. The Provocation test has to be monitored by a specialist as even small doses of Penicllin can lead to Anaphylaxis in children who are truely allergic to it.