Claritin (Loratadine) is an antihistamine that treats symptoms such as itching, runny nose, watery eyes, and sneezing from "hay fever" and other allergies. It is also used to relieve itching from hives. Loratadine does not prevent hives or prevent/treat a serious allergic reaction (anaphylaxis).
Usually, antihistamine tablets start to work within 30 minutes after being taken and tend to be most effective within 1-2 hours after being taken. Antihistamines are more effective when taken regularly as a prevention, before symptoms occur, rather than only when you have symptoms. Claritin (Loratadine)/pseudoephedrine is a combination of two drugs, an antihistamine (loratadine) and a decongestant (pseudoephedrine). Loratadine is a long-acting antihistamine that blocks the actions of histamine that causes some of the symptoms of allergic reactions.