How do antihistamines relieve allergy and sinus symptoms?

Antihistamines block histamines, which are chemicals responsible for many allergy symptoms. Antihistamine medications come in different forms and are available by prescription or over-the-counter. Pills or liquids can be taken orally, nasal sprays can be inhaled, and eye drops can be used. Oral antihistamines can help ease rashes and nasal symptoms caused by allergies. Nasal sprays can relieve nasal stuffiness and sinus congestion. Eye drops help itchy eyes.

Chemicals called histamines are released from some of your body's defense cells, called mast cells. If you suffer from allergies, when you are exposed to these triggers, histamines are released, which cause runny nose, hives, itchiness, etc. Antihistamines are medications that block the histamine chemicals in your body and reduce your allergy and sinus symptoms.

Stacy Wiegman, PharmD
Pharmacy Specialist

Antihistamines stop histamines from attaching to cells and from making those cells leak fluid. In this way, they help to control congestion and drainage that are common allergy and sinus symptoms. Antihistamines are generally split into two categories: First-generation OTC antihistamines and second-generation OTC antihistamines. While they both are used in allergy medications, first-generation antihistamines are sometimes also used in cold and flu medications. Their most common side effect is sleepiness. Second-generation antihistamines are often combined with other drugs to control allergy and sinus symptoms caused by histamines.

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