Antihistamines are a class of drugs that help treat conditions caused by too much histamine, a chemical created by your body’s immune system. They are most commonly used to treat symptoms of allergies, such as congestion, runny nose, sneezing, itching, swelling of the nasal passages, hives, and other skin rashes. Antihistamines come in various forms, including pills, chewable tablets, capsules, liquids, nasal sprays, and eye drops. There are two major subtypes of antihistamines: H-1 receptor antagonists or H-1 blockers, which are used to treat allergy symptoms, and H-2 receptor antagonists or H-2 blockers, which are used to treat gastrointestinal conditions.

Antihistamines work by blocking the effects of histamine, which is released by the immune system in response to allergens. They are available both over-the-counter and by prescription, and some antihistamines cause less sleepiness than others. First-generation antihistamines, which were the first type approved by the FDA, tend to cause more side effects, particularly drowsiness, while newer antihistamines have fewer side effects.

It is important to note that antihistamines may interact with other medications, and some antihistamines may not be suitable for people with certain underlying health conditions. Therefore, it is recommended to talk to a healthcare provider before taking antihistamines, especially if you are taking other medications or have an underlying health condition.