Consuming alcohol while taking Benadryl can increase the side effect of drowsiness, according to MedlinePlus. Therefore, it is best to avoid alcohol during treatment with Benadryl.
Benadryl is classified as an antihistamine, according to MedlinePlus. It treats itchy, watery eyes; runny nose; and sneezing resulting from allergies or the common cold. Benadryl also relieves cough; prevents and treats motion sickness; treats insomnia; and controls abnormal movements in patients with certain movement disorders. While Benadryl effectively treats symptoms, it does not cure the condition causing the symptoms or make patients recover more quickly. It is best for patients with a history of lung problems, glaucoma, ulcers, heart problems or high blood pressure to speak with their doctors before taking Benadryl.
The potential side effects of Benadryl include dry mouth, nausea, vomiting, constipation and loss of appetite, according to MedlinePlus. Headache, nervousness and excitement may also occur. Reporting these side effects is advised if they are severe or persistent. Because Benadryl can cause drowsiness, dizziness and muscle weakness, patients are advised to avoid operating vehicles or heavy machinery until they know how this medication affects them. Vision problems and difficult or painful urination are serious side effects of Benadryl, and they should be reported to a doctor immediately.