When exposed to infection or injury, your body responds defensively, by unleashing an immune response that results in the release of fluids, antibodies and white blood cells to the affected area. This causes inflammation -- the familiar redness, swelling and pain associated with your immune system's attempt to wage war on threats to your well being. Antihistamines are medications that treat inflammation by inhibiting one of the hormones that regulates it.
Mechanism of Inflammation
When your immune system senses a threat due to pathogens, allergens or trauma, it releases histamine, a hormone that causes your blood vessel walls to become more permeable. This increased permeability facilitates the passage of fluids, antibodies and white blood cells out of the blood stream and into the affected tissues. As these additional substances accumulate in the area, the characteristic symptoms of inflammation result.
Effects of Chronic Inflammation
In the short term, inflammation assists your body by helping fight off the offending factors. But when inflammation is chronic it can cause problems of its own. "Time" magazine states that factors such as smoking, high blood pressure, genetic predisposition and diets high in sugar and saturated fat can enable inflammation to continue long after it has outgrown its usefulness, at which point it can become a destructive force and contribute to such diseases as heart disease, diabetes and cancer.
Antihistamines do what their name suggests: They counteract the effects of histamine, which is the initiator of the inflammatory response. The discovery of antihistamines was considered so important that the pharmacologist who first identified them, Daniel Bovet, was awarded the 1957 Nobel Prize. The journal "Clinical Pharmacology and Therapeutics" explains that histamine plays an important role in immune regulation. Antihistamines work by binding to inactive histamine receptors in your body, thus ensuring that they remain inactive. There are two types of antihistamine: first-generation, which includes that found in such commercial brands as Dimetapp and Chlor-Trimeton; and second-generation formulations such as Claritin or Zyrtec.
Antihistamines are commonly taken to combat the effects of inflammation due to allergic responses. They are not commonly used as a treatment for systemic, chronic inflammation. First generation antihistamines may be contraindicated if you have glaucoma, thyroid disease, heart disease and a number of other conditions. If you have liver or kidney disorders, consult your doctor before taking second-generation antihistamines.