What should patients using antihistamines avoid?

Patients using antihistamines should avoid alcohol and other central nervous system (CNS) depressants because these substances can enhance the sedative effects of antihistamines. Many antihistamines, especially first-generation types, can cause drowsiness and sedation as side effects. When taken with alcohol or other sedatives, the risk of excessive sedation, respiratory depression, and impaired cognitive and motor functions increases significantly. This makes it crucial for patients to be aware of the potential risks associated with combining these substances.

The other options, while they may have specific considerations, do not pose a direct and significant risk similar to that presented by the combination of antihistamines with alcohol or other CNS depressants. For instance, eating dairy products or consuming high-caloric foods may not have a major impact on the effectiveness of antihistamines, and while excessive sunlight is something to be cautious of in general for skin health, it doesn't interact specifically with antihistamine function like CNS depressants do.