What is the main action of antihistamines?

Antihistamines primarily work by blocking histamine receptors, specifically the H1 receptors, which play a significant role in the body's allergic response. When an allergen enters the body, histamine is released, leading to symptoms such as itching, sneezing, runny nose, and hives. By inhibiting the action of histamine, antihistamines effectively reduce or prevent these allergic symptoms. This mechanism is what makes antihistamines beneficial for treating allergic reactions, hay fever, and sometimes even motion sickness.

In contrast, other options involve entirely different actions: promoting blood clotting pertains to coagulants, increasing gastric acid production is related to medications that act as proton pump inhibitors, and soothing pain and inflammation is typically associated with nonsteroidal anti-inflammatory drugs (NSAIDs). Therefore, the correct answer focuses on how antihistamines directly block the effects of histamine, leading to a decrease in allergic reactions.