Is antibiotic different from antihistamine

An antibiotic acts by helping to kill or inhibit the growth/reproduction of fungi, bacteria, and protozoa. These are not to be confused with anti-virals, that specifically target viral infections and work by means of a different mechanism.

Antihistamines, on the other hand, are medications that inhibit your body's histamine response to allergens. Specifically, by inhibiting the release of the histamines in your body, not specifically by targeting or annihilating them.

Antibiotics are used to fight bacterial infection, sometimes for specific infections or sometimes as a precaution against infection in the case of surgery or injuries that can leave the body susceptible to disease (compound fractures, etc).

Antihistamines are used to treat the symptoms of allergic reactions, and can additionally increase the risk of infection, as histamine production is one method of fighting infection. Sometimes both are prescribed together to treat symptoms and cause, but this can be dangerous as the side-effects are often cumulative.