What is the main action of antihistamines in the body?

Antihistamines primarily function by opposing the action of histamine in the body. Histamine is a compound released during allergic reactions and inflammatory responses, leading to symptoms such as itching, sneezing, and nasal congestion. When antihistamines are administered, they bind to histamine receptors, particularly the H1 receptors, effectively blocking histamine from exerting its effects. This blockade reduces the typical symptoms associated with allergies and helps alleviate discomfort caused by the overactivity of histamine.

Promoting sweating is not a function of antihistamines; rather, they can sometimes have drying effects due to their action on mucus membranes. While constricting blood vessels and suppressing coughing are important physiological processes, they are not the direct actions of antihistamines. Instead, antihistamines are primarily concerned with mitigating the actions of histamine, which is why being able to recognize their main role is crucial for understanding their use in treating allergic reactions and conditions like hay fever.