What side effect should a client be aware of when prescribed diphenhydramine?

A. Sneezing: Sneezing is a symptom of allergic reactions or upper respiratory irritation, not a side effect of diphenhydramine. The medication is intended to reduce allergic symptoms, including sneezing, rather than cause it. B. Redness of the eyes: Redness of the eyes is typically related to allergies or irritation. Diphenhydramine may actually help relieve eye redness caused by allergic reactions, not induce it. C. Hives: Hives are a manifestation of an allergic reaction. Diphenhydramine is used to treat hives, so their presence would not be an expected side effect of the medication. D. Dry mouth: Dry mouth is a common anticholinergic side effect of diphenhydramine. The medication blocks muscarinic receptors, reducing salivary secretions, which clients should be educated to manage through hydration or sugar-free lozenges.