What symptom is typically associated with an allergic reaction to medication?

A skin rash is a common and well-recognized symptom of an allergic reaction to medication. Allergic reactions occur when the immune system mistakenly identifies a medication as a harmful substance, leading to a response that can manifest in various ways. A skin rash, often appearing as hives or generalized redness, is one of the body's ways to react to allergens, and in many cases, it indicates that the immune system is actively reacting to the substance.

The other symptoms described, while they can be associated with medication side effects, are not exclusive indicators of allergic reactions. Nausea can occur due to numerous reasons, including gastrointestinal upset or as a side effect of the medication itself. Coughing may be a reaction but is more often linked to respiratory conditions or sensitivities rather than allergic reactions specifically. Finally, dry mouth may arise from various factors, including medications affecting saliva production, rather than being a direct allergic response. Therefore, a skin rash stands out as the most characteristic symptom associated with an allergic reaction to medication.