Yes, dogs can take certain human antihistamines, such as Benadryl (diphenhydramine), Zyrtec (cetirizine), and Claritin (loratadine), but only under the express guidance of a veterinarian.
Diphenhydramine (Benadryl®), cetirizine (Zyrtec®), and loratadine (Claritin®) are commonly used antihistamines that relieve allergy symptoms or counteract allergic reactions in humans. Antihistamines are usually safe for dogs but can make some dogs drowsy and others hyperactive.
Frequently asked questions about antihistamines for dogs
The recommended dose for Benadryl in dogs is 2-4 mg/kg of body weight every 8-12 hours. Higher doses greater than 5 mg/kg can have toxic side effects such as seizures, respiratory depression, and cardiovascular effects.
Can I give my dog claritin or zyrtec for allergy relief? If so, what No, I would not advise using either of these drugs. Histamine reactions are a very small part of the dog's allergy problems, so these antihistamines will not help, unless there is an acute reaction like a bee sting, fireants, or a vaccine reaction.
Cetirizine is considered safe for most dogs. Speak with your vet first to ensure this medication is appropriate for your dog. It is important to only use products that contain cetirizine as the sole active ingredient and avoid human combination products that contain other ingredients that may be toxic to animals.
Zyrtec has become the new first-line drug for dog allergy, largely because of its convenient dosing schedule. Although individual response to antihistamines does vary greatly, this year our clients are seeing a higher response rate than with Benedryl.
fexofenadine (Telfast®) – this is a second gen. It is available as 60 mg capsules and 120 or 180 mg tablets. The dose is 5–10 mg/kg once or twice daily (don't use if your dog is on ketoconazole or a macrolide antibiotic)
Allergy medicines that are safe for your pet include:
Cetirizine (ZYRTEC): 0.25-mg to 0.5-mg per pound for dogs, 5-mg total for cats. These can be given once daily, preferably in the evening. It is available in 5-mg and 10-mg tablets. Do not use with other nervous system sedatives like phenobarbitol.
Which is stronger: Zyrtec or Claritin? Zyrtec is often considered stronger and faster-acting, but it may cause more drowsiness. Claritin is less sedating and works well for mild allergies. The best choice depends on your symptoms and how your body reacts.
Over-the-counter antihistamines like Zyrtec can sometimes help dogs with mild allergy symptoms. Common symptoms include itching, sneezing, and skin irritation. Diet changes or prescription medications may be necessary for chronic issues. Never give your dog medications without talking to your veterinarian first.
Benadryl can be dangerous for your dog if you give too much. An overdose of Benadryl can cause seizures and other side effects. The safest way to give Benadryl is to give it according to the weight of your dog. AKC says the dose for Benadryl is 2 to 4 milligrams per kilogram of body weight, two to three times per day.
This human medication is used off-label for dogs.
If your dog reacts to a bug bite or has allergies and itches, your veterinarian may recommend Zyrtec to help make him comfortable. Zyrtec (generic name is cetirizine) is a human antihistamine drug and is used “off label” for dogs, as it is not FDA-approved for dogs.
Zyrtec (Cetirizine): A popular & safe antihistamine that can be effective in reducing itching and inflammation in dogs. Claratyne (Loratadine): Similar to cetirizine, loratadine can help relieve itching and allergic symptoms in dogs.
Benadryl can be used to treat itchy skin in dogs caused by skin allergies. It also reduces many of the other symptoms of allergies. However, check with your veterinarian for the correct dosage based on your dog's weight and if it might interact with other medication it is taking.
According to the Merck Veterinary Manual, the standard dose for Benadryl is 2–4 milligrams per kilogram of body weight, or 0.9–1.8 milligrams (mg) of Benadryl per pound. Therefore, a simple and practical dose is 1 mg of Benadryl per pound of your dog's weight, given two to three times a day.
Cetirizine (Zyrtec®, Reactine®) is an antihistamine used to treat and prevent pruritus (itching) associated with atopic dermatitis, urticaria (hives), and insect bite reactions in cats and dogs. It may also be used for respiratory allergy symptoms. Its use in cats and dogs is off label (extra label).
Quercetin, often referred to as "Nature's Benadryl," is considered one of the best natural antihistamines for dogs. It's a bioflavonoid compound that can help reduce allergic reactions and inflammation.
Cetirizine is a non-drowsy antihistamine used to treat itchy skin (pruritus) in dogs due to atopic dermatitis or allergens. The standard cetirizine dosage for dogs is 1 milligram per kilogram of body weight (0.45 mg/lb) or 10–20 mg/dog every 12–24 hours.
Allergex is Chlorpheniramine. Antihistamines are generally well tolerated in dogs and can be used for both short and long-term treatment without the complications associated with other medications like steroids.
Chlorpheniramine is an over-the-counter human antihistamine that can be given to dogs and cats with allergies or itching associated with certain types of skin hypersensitivity.
For this reason we recommend a consultation with our vets to discuss how to best manage their symptoms. If a visit to us is not possible you can try dosing your pet with a human antihistamine – we would recommend Zyrtec at a dose of 10mg per 10kg daily.
EFFECTS OF TOXICITY
Large doses of antihistamines can lead to disruption of intestinal smooth muscle function causing gastrointestinal upsets. They can also suppress the respiratory system and impact on the nervous system, causing sedation or excitement.
Top 7 Human Medications That Can Be Safe for Cats and Dogs (With Vet Guidance)