What is a common sign seen in a patient with an allergic reaction?

Hives, also known as urticaria, are a common sign of an allergic reaction. They manifest as raised, itchy welts on the skin and can vary in size and shape. This reaction occurs as the body releases histamines in response to an allergen, which causes inflammation and other symptoms associated with allergies.

The presence of hives can be an important indicator for healthcare providers when assessing a patient for an allergic reaction, as they may signal that the patient is experiencing a systemic response to an allergen. In more severe cases, such as anaphylaxis, hives may accompany other symptoms such as difficulty breathing and swelling of the throat.

While the other options suggest possible physiological changes, they are not typically associated with allergic reactions. For instance, increased blood pressure generally does not correlate with the vascular response of allergic reactions and can even be inconsistent. Dry mouth might occur due to anxiety or medication rather than a direct effect of allergies, and a decreased heart rate is less common; allergic reactions usually lead to increased heart rates as the body responds to stress or anaphylaxis rather than a decrease.