Which one of the following is antihistamine?

Diphenyl hydramine

The answer is 2. diphenhydramine.

Diphenylhydramine is an antihistamine that is used to treat allergies, such as hay fever, hives, and allergic rhinitis. It is also used to treat motion sickness and nausea. Chloramphenicol is an antibiotic, norethindrone is a birth control pill, and omeprazole is a proton pump inhibitor. None of these drugs are antihistamines.

Diphenylhydramine works by blocking the action of histamine, a chemical that is released by the body during an allergic reaction. By blocking the action of histamine, diphenhydramine can reduce the symptoms of an allergic reaction, such as itching, sneezing, and runny nose.

Diphenylhydramine is generally safe when used as directed. However, it can cause some side effects, such as drowsiness, dizziness, and headache. It can also interact with other drugs, so it is important to talk to your doctor before taking diphenhydramine.