What is a common side effect of antihistamines like Diphenhydramine?

Antihistamines, such as Diphenhydramine, are commonly associated with xerostomia, which is dry mouth. This side effect occurs because antihistamines block histamine receptors that can help keep the salivary glands functioning properly. As a result, the reduction in saliva production leads to a sensation of dry mouth, which can be uncomfortable and can increase the risk of dental issues such as cavities and gum disease.

In contrast, insomnia, headache, and increased appetite are less frequently related to the use of antihistamines like Diphenhydramine. While some antihistamines can cause drowsiness and may be used for their sedative effects, others may not directly contribute to insomnia. Headaches can arise from a variety of factors and are not a defining characteristic of antihistamine use. An increase in appetite is not a typical side effect associated with this class of medication.