What to do?
If there is a suspicion that the skin rash was caused by taking penicillin, the antibiotic should be discontinued immediately or, after a positive allergy test, not prescribed again by a doctor. Since penicillin belongs to the drug family of the so-called beta-lactams, an antibiotic of a different class (e.g. macrolides, quinolones, glycopeptides) should be chosen if a bacterial infection is to be treated again. For the treatment of penicillin rashes, a glucocorticoid ointment (cortisone ointment) can be prescribed by the doctor and applied to the affected skin areas. If there are severe allergic reactions – i.e. in addition to the rash – such as severe itching, shortness of breath or swelling of the face, an antihistamine should be taken to reduce the excessive reaction of the immune system.
Duration of rash after penicillin
After the penicillin is removed or stopped, the rash should disappear within one to two weeks. A cortisone treatment can speed up the time to normalization of the skin somewhat, but should only be used in extreme skin reactions because of the side effects. Often the rash disappears without leaving any traces. However, after the exanthema has healed, temporary grayish discoloration of the skin may occur. As already mentioned, in the case of a skin rash after penicillin, it is advisable to avoid taking the medication again, as otherwise it is highly likely that a new rash or other, sometimes life-threatening reactions such as shortness of breath will occur.
How do allergy and intolerance differ?
Drug intolerance is a type of allergy. There is also the pseudoallergy, in which similar symptoms can occur. However, the two terms differ in the mechanisms that take place in the body.
In an allergy, the immune system is directly involved and forms antibodies against the drug. In the case of a pseudoallergy, ingredients of the drug act directly on certain cells of the body, such as mast cells, without any immune reaction: Histamine is released and a so-called pseudoallergic reaction with symptoms such as skin rash, swelling, shortness of breath or diarrhea occurs. It should also be noted that in the case of a genuine allergic reaction, even small amounts of penicillin usually cause a physical reaction such as a skin rash. In the case of an intolerance, larger quantities of the drug are usually necessary for a physical reaction and it usually proceeds milder than an allergy.