“Benadryl is a great medication for use in dogs with mild-to-moderate allergies. Seasonal allergies, food allergies, environmental allergies, and allergic reactions to snake and insect bites all respond to Benadryl in most cases.” https://www.akc.org/expert-advice/health/benadryl-for-dogs/
Benadryl - a milligram per pound of body weight.
Do not give Benadryl to dogs with glaucoma, high blood pressure or cardiovascular disease.
“1 mg per pound of body weight, given 2-3 times per day.
If your dog has any of the following conditions, only use Benadryl after consulting your veterinarian:
Angle closure glaucoma
Bladder neck obstruction
Allergic lung disease