How Antihistamines Work in the Body

Antihistamines are a class of drugs designed to block the chemicals in the body that result in the irritation and swelling associated with allergies and other ailments. Histamines are naturally occurring compounds that are produced by the immune system in the body. They have many biological uses that help the body to fight off diseases and infections. Histamines are released whenever an allergen like pollen or an irritant enters the body and they bind with receptors and trigger itching, swelling, and fluid production in order to flush out the allergen or irritant. Antihistamines work by covering the receptors so that the histamines are unable to trigger a reaction.

Antihistamines are available in several forms. The most common form is a simple pill or capsule. First-generation antihistamines are considered safe and are sold over the counter without requiring a prescription. Antihistamines are also available in a liquid form that can be sprayed into the nostrils, dropped into the eyes, or consumed like a beverage. The most modern generation of antihistamines can be injected, used as a nasal spray, or taken as a pill. Most of the new antihistamines are only available with a prescription.

Anyone who needs to use an antihistamine in order to treat allergies should take the drugs at least one hour before exposure. Taking antihistamines after symptoms have started to appear does not always have a noticeable effect because the histamine receptors are already in use and cannot be blocked. The drugs are preventive although they are effective during long-term exposure to allergens and for certain types of swelling related to an allergic reaction. Antihistamines do not always stop all of the symptoms that occur. They are commonly combined with other types of drugs that help with decongestion and pain relief.

The role of histamines in the body is complex and covers several areas. Suddenly blocking histamine receptors causes several side effects because of this. The main side effect from first generation antihistamines is drowsiness that can last for hours. This also results in confusion in some people. Dry mouth, dizziness, and nausea could occur as well. The side effects can become very pronounced in some individuals. This is why the over-the-counter medications have so many warning about driving or using heavy machinery while taking the drug. The newest antihistamines target very specific receptors. This has resulted in several prescription medications that stop allergy symptoms without causing drowsiness or other side effects.