When your body comes into contact with whatever your allergy trigger is -- pollen, ragweed, pet dander, or dust mites, for example -- it makes chemicals called histamines.
In the first part of the 20th century, the pharmacotherapy of anxiety and insomnia relied on barbiturates, which were replaced with benzodiazepines as drugs of choice in the second part of the previous century.
Antihistamines work by blocking the effects of a chemical called histamine that is responsible for many allergic symptoms.
Patients who experience significant allergic symptoms regularly may take daily antihistamines to keep their symptoms under control.
Newer antihistamines have fewer side effects, so they may be a better choice for some people.
Some of the main side effects of antihistamines include: If you take an antihistamine that causes drowsiness, do so before bedtime.