Can dogs have Benadryl?

Benadryl (diphenhydramine) is a human antihistamine often used off‑label in dogs to relieve allergy symptoms, itching, swelling, motion sickness, and anxiety. Veterinarians may recommend it when dosed appropriately and only after checking for contraindications.

What is Benadryl used for in dogs?

• Seasonal, food, or skin allergies (itching, hives, swelling)
• Respiratory allergy signs (coughing, sneezing, runny nose, watery eyes)
• Mild sedative for anxiety or travel
• Motion sickness (nausea, vomiting)
• Mast cell tumor reactions (histamine release)

How does Benadryl work in dogs?

Diphenhydramine blocks histamine receptors, reducing allergic inflammation and itching. It also acts on central receptors to help control nausea and vomiting from motion sickness.

What is the Benadryl dosage for dogs?

Veterinary guidelines recommend 2–4 mg/kg (0.9–1.8 mg/lb) by mouth 2–3 times daily. A simple regimen is 1 mg per pound of body weight, 2–3 times a day. Injectable dosing is 0.5–2 mg/kg intramuscularly as directed by a veterinarian.

What are the side effects of Benadryl in dogs?

• Drowsiness or sedation
• Unsteady gait
• Dry mouth
• Rapid breathing
• Excess salivation
• Urinary retention

Less common: diarrhea, vomiting, anorexia.

Can your dog overdose on Benadryl?

Yes. Overdose signs include rapid heart rate, agitation, constipation, dilated pupils, hyperthermia, tremors, seizures, and coma. Seek emergency veterinary care if these occur.

Is Benadryl safe for every dog?

Use with caution or avoid if your dog has lung or heart disease, liver impairment, glaucoma, seizures, urinary obstruction, is pregnant, or is on MAO inhibitors or certain antifungals. Always consult your veterinarian first.

Can dogs take liquid Benadryl?

Only if the formulation contains no alcohol or xylitol. Check labels and confirm with your vet before using liquid products.

Are there other antihistamines that are safe for dogs?

• Claritin (loratadine)
• Zyrtec (cetirizine)
• Chlor-Trimeton (chlorpheniramine)
• Vistaril (hydroxyzine)

No one antihistamine is proven superior; choice depends on cost, dosage form, and side effect profile. Consult your vet for recommendations.

Sources

• American Kennel Club. Benadryl For Dogs: Uses, Side Effects, and Dosage Information. Updated Jun 28, 2024. Accessed Mar 5, 2025.
• Merck Veterinary Manual. Antihistamine Dosages for Integumentary Disease in Animals. Accessed Mar 5, 2025.
• WebMD. Can I Give My Dog Benadryl? Accessed Mar 5, 2025.