How do allergic reactions to medications typically develop?

Allergic reactions to medications often develop through a process known as sensitization, which can take time. When a person is first exposed to a medication, their immune system may not react immediately; instead, it may take one or more exposures to the drug before the immune system recognizes it as a foreign substance. This recognition can lead to an allergic response upon subsequent exposures.

The phenomenon of sensitization explains why many individuals may tolerate a medication initially but then develop an allergy after multiple uses. This gradual sensitization process can culminate in various allergic symptoms ranging from mild to severe during later exposures.

In contrast, other choices present inaccuracies about the nature and timing of allergic reactions. Some allergic reactions can indeed occur immediately upon the first dose in rare cases, but this is not the typical case for most allergies. Furthermore, while some allergic reactions might be mild, they can also be severe and cannot be classified generically as always mild. Lastly, allergic responses can develop with repeated doses, contradicting the notion that they cannot occur under those circumstances.