What are common side effects of antihistamines?
Since the first generation antihistamines can penetrate the brain tissue, they generally cause more side effects than the second generation drugs, which usually cannot enter the central nervous system. Drowsiness is the most noticeable side effect, but this is sometimes desirable. For example, it may be useful when nighttime symptoms prevent restful sleep. During the day, however, this effect can cause problems. Allergy Alert Be cautious about driving a car or operating a machine when using OTC antihistamines. Do not take any tranquilizers or drink alcohol along with these drugs. The combination may promote more drowsiness. Also, check with your doctor before taking an antihistamine if you have glaucoma or thyroid, heart, or prostate problems. The first generation antihistamines may also cause troublesome anticholinergic effects such as heart palpitations, difficulty urinating, constipation, dry mouth, and nervousness. These side effects usually occur when the medication is taken at hi
