What symptom might indicate an allergic reaction that antihistamines are meant to prevent?

Antihistamines are specifically designed to combat allergic reactions by blocking the action of histamine, which is a substance released during an allergic response. Symptoms that are indicative of allergic reactions include hives, itching, swelling, sneezing, runny nose, and other respiratory issues, all of which result from the overactivity of histamine in the body. Since antibacterial and antiviral medications do not affect allergic reactions, the correct answer reflects the purpose of antihistamines, which is to alleviate these allergic type reactions.

Other symptoms like nausea, fever, or muscle pain may indicate various conditions such as infections or other types of illness but are not directly associated with allergic reactions. Antihistamines would not be effective in treating such symptoms, which further underscores the focus of antihistamines in managing allergic reactions specifically.