Will Benadryl Make My Dog Sleepy?

One of the side effects of Benadryl is drowsiness, which helps to calm anxious dogs. The Merck Veterinary Manual states that diphenhydramine may relieve symptoms of mild-to-moderate anxiety in pets associated with travel. It also may help relieve motion sickness.

How long does it take for Benadryl to make a dog sleepy?

The injection is typically given in the hospital, either in the vein, muscle, or under the skin. This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

Do dogs get sleepy with Benadryl?

Potential Side Effects and Risks of Benadryl

Benadryl can make a dog very sleepy, cause dry mouth or urinary retention, and potentially cause some gastrointestinal upset such as diarrhea and/or vomiting. In cats, it may cause the opposite of what it's used for—called a paradoxical effect—and you may see excitement.