tl;dr.. antibiotics and allergy. Or allergy and antibiotics.
Definitely looks like an allergy reaction to antibiotics, and as far as I know the penicillins are the most common cause for that. Other antibiotics can cause similar reactions, other types of medication as well. In the following discussion I concentrate on penicillins. Allergic reactions to other antibiotics follow the same pattern, but as said, penicllins are the most common cause, and also the most commonly used antibiotics. My guess is that you were treated with a penicillin, but it's not 100%, and it's important to know what you got. Observe that there are different kinds of penicillins, and if you react to one of them, you react to all of them. But not to antibiotics other than penicillins, except maybe a few chemically closely related drugs (cephalosporines).
There are two types of allergy reactions to penicillin.
- Immediate allergic reactions come within minutes/an hour after the first dose. These reactions is caused by a specific type of antibodies, the IgE, and involves the release of histamine. It is the same type of allergy behind hay fever (treatable by antihistamines). Usually reactions are mild, but annoying. But it can also cause (rarely) an acute severe, life threatening reaction, the anaphylactic shock (treated by injection of adrenaline). Same reaction can (also rarely) happen after vaccines which is why you usually have to wait 20 minutes or so before leaving the premises. If you've had an immediate reaction (even if mild), next time a more serious reaction can occur, so penicillins are contraindicated (must not be used). OTOH, reactions to other agents, like pollen in hay fever does not exclude use of penicillin.
- Delayed allergic reactions, which is what you have, come days after starting the treatment, sometimes even after ending it. These reactions are not caused by IgE, in stead T-cells are involved. Fortunately anaphylactic shock is not an issue here, but unfortunately other dangerous conditions may occur (but fortunately not very common).
So, in both cases you should avoid the specific antibiotic. Ideally the allergy should be confirmed by tests, but I don't know if that is available (wasn't when I left med school). Having to avoid penicllin is unfortunate, because penicillin is a very good antibiotic for infections treatable by it, with few serious side effects other than allergy. For instance, a normal daily dose of the penicillin used (phenoxymethylpenicillin) for upper airway infections is around 3 g. For meningitis, at my hospital back then we used doses 10 times as high. Other antibiotics are available, however.
pibbuR who unlike his wife does not react adversely to penicillins.
PS. I said there are different kinds of penicillins. Phenoxymethylpenicillin is the one most commonly used, and works well against bacteria causing pneumonia, upper airway infections and meningitis. But it doesn not work against for instance germ causing urinary infections. Another type of penicillin, ampicillin is a so called broad spectered antibiotic, works against many more bacteria, including those responsible for urinary infections. And we have cloxacillin which works against staphylococci resistant to other penicillins. There are more.
One thing that may cause confusion is that the companies making drugs put their own name on their products. In Norway we have Apocillin, Weifapenin, Femepen etc (Note the capital first letter), which all contain phenoxymethylpenicillin. I don't know the names used abroad. DS
PPS. In Norway, and I suspect most other countries, an allergic reaction to penicillins should be presented very prominently in the EPR, as so called "cave information" ("cave" means AFAIR(emember), didn't check, "be very careful"), so it should not be possible to overlook it. However, (depending on the jurisdiction) the EPR isn't always shared between hospitals, and with primary care, so the patient should also know the specifics. DS.
PPPS. One more thing. Allergy is by definition a hypersensitivity reaction caused by the immune system. There are other types of hypersensitivity. Intolerance to lactose in milk,for instance, is a reaction caused by lack of the enzyme lactase in the gut. So while you are hypersensitive to lactose, you're not allergic to it. Lactose intolerance can not cause an anaphylactic reaction. Intolerance to milk proteins OTOH is an allergy, and therefore potentially dangerous. DS.
PPPPS. No more PS's. Promise!!"! DS.