Antihistamines work by blocking the action of histamine which the body produces as part of its natural defences.Histamine is released as a reaction to foreign substances (allergens), and starts a chain reaction that leads to the release of other chemicals that add to the allergic response. There are two different types of antihistamine; sedating antihistamines, which can enter the brain and cause drowsiness and non-sedating antihistamines which do not.In common use, the term "antihistamine" refers only to H In type I hypersensitivity allergic reactions, an allergen (a type of antigen) interacts with and cross-links surface Ig E antibodies on mast cells and basophils.Once the mast cell-antibody-antigen complex is formed, a complex series of events occurs that eventually leads to cell degranulation and the release of histamine (and other chemical mediators) from the mast cell or basophil.In turn, they decrease the symptoms of the allergy.Zyrtec and Claritin have very few side effects and are generally recognized as safe for most people. Zyrtec can cause sleepiness, but only in some people.
Additional administration of epinephrine, often in the form of an autoinjector (Epi-pen), is required by people with such hypersensitivities.When your body encounters something it’s allergic to, it sends out white blood cells and goes into fight mode. This substance causes many of the symptoms of an allergic reaction.Antihistamines are designed to block the effects of the histamine that your body produces.They reported that out of 390 CU patients who were treated with antihistamines 44% responded well, 29% became asymptomatic, and 15% showed partial improvement.In a recent paper from Japan it was observed that the improvement rates (defined as a urticaria symptom score UAS ≤ 3) in 117 CU patients who received standard doses of AHs were 36.6% at 12 months, 51.2% at 24 months, and 66.1% at 60 months, while the remission rates were 11.5%, 13.9%, and 27.7%, respectively .These factors could determine which of these two drugs is better for you. However, newer antihistamines like Zyrtec and Claritin are less likely to cause this side effect. Most people experience at least 24 hours of relief after a single dose. People who take it may feel relief in as little as one hour.