Antihistamines help reduce the sneezing, runny nose and itchiness of allergies.
They're more useful if you use them before you're exposed to allergens. You can buy some antihistamines without a prescription. These relieve symptoms just as well as prescription medicines do, but they tend to cause drowsiness and dry mouth. This often improves after 1 to 2 weeks of regular use. Antihistamines that require a prescription from your doctor are less likely to cause tiredness or dry mouth.