Loratadine treats symptoms of seasonal allergies, such as runny nose, sneezing, watery eyes and scratchy throat, according to Drugs.com. Also known by the brand names Alavert, Claritin, Dimetapp ND, Tavist ND and Wal-itin among others, loratadine works by reducing the effects of histamine in the body.
The usual adult dosage for loratadine is 10 milligrams daily, but individuals should follow a doctor's instruction, advises Drugs.com. Possible side effects of loratadine include headache, drowsiness, stomach pain, dry mouth and nervousness. Reactions such as a fast or uneven heart rate, a severe headache, light-headedness, hives, or difficulty breathing require immediate medical attention.