What is an example of an adverse effect?

An adverse effect refers to an unintended and harmful reaction to a medication or treatment. In this context, a rash developing from taking penicillin is classified as an adverse effect because it is directly linked to the administration of the medication. This kind of reaction occurs as a result of an individual's sensitivity or allergic response to penicillin, demonstrating the potential negative outcomes that can arise when using certain drugs.

In contrast, the other options provided do not fit the definition of an adverse effect related to medication or treatment. Swelling from a bee sting is a natural response to an allergen rather than a consequence of a drug; breaking a bone in an accident involves a physical injury not caused by a medication; and a headache from dehydration is a symptom resulting from lack of fluid intake, not from a drug's effect. Therefore, the reaction tied to penicillin is undeniably an example of an adverse effect in the context of pharmacological treatments.