Hi, welcome to the forum, few of the antibiotics can cause allergy and are mediated by release of histamine in the body.
The spectrum of these reactions can vary widely; reactions may present as typical allergic symptoms (eg, itching, urticaria, rash, edema) after a single dose, or may manifest as severe idiosyncratic dermatologic reaction, pulmonary (eg, pneumonitis), renal (eg, nephritis), hepatic (eg, hepatic failure or necrosis), and/or hematologic (eg, anemia, cytopenias) events, usually after multiple doses.
If drug allergy is suspected you need to discontinue the drug and report to your doctor immediately. Another antibiotics can be started. Treatment includes anti histaminic and glucocorticoids against prescription. Even shot of adrenaline has to be given, when one is in anaphylactic shock. I suggest you to consult your physician. Take care and regards.
Anbitiotics should NOT be prescribed or taken for allergy symptoms - only when there is an infection present. Not only are the antibiotics hard on your stomach/disgestive system, overuse of them can make them much less effective when you really need them. Therefore, they should only be taken when a confirmed infection is present.
When you do have to take them, if you're speaking of digestive troubles while on them, there are some things you can do - definitely take them with food, unless specifically instructed not to. Also, since they can be tough on the tummies, don't lay down for at least two hours after taking them - this will help lessen the chance of reflux and can help avoid some of the tummy upsets so common with antibiotics.
Sometimes women can also get yeast infections from taking antibiotics. If you're prone to this, you can either request a different antibiotic (one that is less likely to cause this) or ask your doctor if there is something he/she can give you along with the antibiotic to reduce the likelihood of getting a yeast infection. The reason the yeast infection happens is that the antibiotic kills off not only the bad bacteria, but also the "good" bacteria that is always present in our bodies - and this can cause an overgrowth of yeast, sometimes in our stomachs, but more often in the urinary tract. There are also over the counter medications that can be used if you start getting a yeast infection, however, before using anything, check with your doctor or pharmacist to make sure it's ok to use with the antibiotic.
The most important thing is to remember to ONLY use antibiotics when there is a definite infection going on and NOT for viruses or allergies. Sometimes constant allergies can lead to an infection, and if you're finding that you are getting a lot of sinus infections, etc., you may want to seriously consider other options for treating your allergies that would be more effective and could hopefully keep you from getting the infections in the first place.
Hope you feel better --
A fellow allergy sufferer