What is a common symptom of a drug allergy?

A common symptom of a drug allergy includes rash or difficulty breathing, which are indicative of an immune response to a drug. When the body perceives a medication as a harmful substance, it can trigger an allergic reaction. This immune response may manifest in various ways, with skin rashes being a frequent sign. The rash can vary from mild hives to more severe skin reactions.

Difficulty breathing is another serious symptom that can occur, often resulting from anaphylaxis, a potentially life-threatening reaction that requires immediate medical attention. The presence of either rash or respiratory distress highlights the body's hypersensitivity to the medication and indicates that the individual is experiencing an adverse allergy-related event.

The other options, such as increased heart rate, nausea, and headache, can be associated with side effects of medications but are not specific indicators of an allergic reaction. While they may occur in some situations, they do not specifically signal an allergic response in the way that a rash or difficulty breathing does. This specificity makes rash or difficulty breathing the correct response for identifying common symptoms of a drug allergy.