How Antihistamines Help in Allergies

Allergic reactions happen when your body is exposed to external chemicals (normally harmless ones), called allergens, which can start a series of responses from the immune system. Your immune system’s primary job is to protect you from diseases caused by invading viruses and bacteria. Sometimes, harmless proteins or chemicals are mistakenly attacked by you immune system. Antibodies are released in the blood to mount an attack to the threat. As part of this complex process, a mast cell--a type of blood cell--produces histamine.

Histamines are powerful stimulant that can cause localized or general irritation is a certain part of the body or all throughout. The resulting reactions are far worse than the effects of the threat inside the body. Common allergic reactions due to histamine action are itchy and watery eyes, runny nose, skin rashes, vomiting, diarrhea, and constriction of the airways. In some rare cases, antihistamine secretion can cause anaphylaxis, a life-threatening medical condition that shuts off the airways and affect multiples organs at once.

Antihistamines prevent the production of histamines in the body. They do this by blocking the receptors of cells that are involved in histamine production process, thereby preventing the allergic reaction from taking place.