What is a key warning to give to someone taking Benadryl?

Drowsiness is a key warning to give to someone taking Benadryl (diphenhydramine) because it is an antihistamine known for its sedative effects. This medication is often prescribed to alleviate allergy symptoms, but one of its most significant side effects is causing drowsiness or sleepiness. Due to this sedative property, individuals taking Benadryl should be cautious about engaging in activities that require full alertness, such as driving or operating heavy machinery. Recognizing this side effect is essential for user safety and proper medication management.