Popular over-the-counter antihistamines include Benadryl, Claritin, Chlor-Trimeton, and Zyrtec. Antihistamines are usually the first drugs to use when a person experiences allergies. They work by blocking the production of histamine, a substance the body produces when it comes in contact with an allergen, according to WebMD.Continue Reading
Histamines cause swelling of the nasal tissues, watery eyes and itching of the mouth. In some instances, they cause itchy rashes or hives, reports WebMD. Reducing the production of histamine reduces the allergic reaction. The medication provides help with seasonal, indoor and food allergies but do not relieve all the symptoms. Doctors sometimes suggest patients take a decongestant along with the antihistamine to treat a stuffy nose from seasonal allergies. Medications such as Claritin-D and Zyrtec-D provide the combination in a single tablet.
Antihistamines are available as tablets, liquids, nasal sprays and eye drops, according to Mayo Clinic. The sprays help to relieve sinus congestion and the eye drops help to reduce itchy, watery eyes due to allergies.
Antihistamines often cause drowsiness, reports Mayo Clinic. The potential for drowsiness is severe enough that a person using the medication should not drive a car or operate heavy machinery. Some users find the eye drops sting their eyes. Storing the drops in the refrigerator helps to reduce this side effect.Learn more about Medications & Vitamins