Other safe antihistamines for dogs include Claritin (loratadine) and Zyrtec (cetirizine). They produce less sedation than Benadryl does but could still make your dog drowsy. Warning: Make sure your OTC allergy medicine only contains antihistamines.
If Benadryl doesn't work for your dog, there are other OTC antihistamines available, including hydroxyzine, loratadine (brand name Claritin), chlorpheniramine, clemastine, fexofenadine, and cetirizine (Zyrtec). Talk with your veterinarian about which option is best for your dog, and the correct dosage to administer.
Zyrtec is an over-the-counter human allergy medication sometimes given to dogs with atopic dermatitis or mild to moderate environmental allergies. Vets may recommend Zyrtec for dogs who scratch excessively, are sensitive to insect bites, or have dermatitis.
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. Its use is in cats and dogs is 'off-label'. Many drugs are commonly prescribed for off-label use in veterinary medicine.
Alternatives to Benadryl for dogs.
If your dog reacts poorly to Benadryl but needs regular allergy treatment for a seasonal allergy, there are some alternatives you can use. Both cetirizine (Zyrtec) and loratadine (Claritin) are considered safe for dogs in the right dosage.
Antihistamines with the active ingredients of diphenhydramine, chlorpheniramine, cetirizine, clemastine or loratadine are usually safe for most healthy adult dogs. Hydroxyzine is another dog-safe antihistamine and one of the most effective available, but it's only available on prescription.
You can safely give Zyrtec to your dog up to 20 mg per day.
Pet allergy relief
ZYRTEC® starts working at hour 1 and stays strong day after day, so you can reduce your cat and dog allergy symptoms.
Diphenhydramine (Benadryl): 1mg per pound (one 25mg tablet for a 25lb dog) twice daily. Cetirizine (Zyrtec) ¼ - ½ mg per pound (one 10mg tab per 30-40 lbs) twice daily.
#1 Overall Best: Veterinary Formula Clinical Care Hot Spot & Itch Relief Spray. After plenty of research, we've found that the overall best anti-itch product for dogs is the Veterinary Formula Clinical Care Hot Spot and Itch Relief Spray.
Zyrtec is a popular second-generation antihistamine first prescribed to people. However, more and more veterinarians have started prescribing it to dogs in pain with pruritus caused by allergic dermatitis. The reason for this is Zyrtec is rather low-risk, however, it's not as effective as the drug Apoquel.
Diphenhydramine (Benadryl®), cetirizine (Zyrtec®), and loratadine (Claritin®) are commonly used antihistamines that relieve allergy symptoms or counteract allergic reactions. Antihistamines are usually safe but can make some dogs drowsy and others hyperactive.
A main difference between Benadryl and Zyrtec is that Zyrtec tends to cause less drowsiness and sedation than Benadryl. Both Benadryl and Zyrtec are available in generic form and over-the-counter (OTC).
While Benadryl is not yet FDA-approved for veterinary use, it is considered safe for use in dogs and cats and is commonly used in veterinary practices across the U.S.
Zyrtec is a second-generation antihistamine, which means that it will not cause your canine companion to be drowsy or fatigued. Zyrtec is active for up to 24 hours, so your dog will be free from a runny nose, itchy skin, sneezing, and other symptoms for the whole day.
Cetirizine has not been proven safe to use in dogs or cats that may be pregnant or nursing. Cetirizine comes in tablet form and should be taken orally once a day. For dogs, dosage is based off of their overall weight, the ratio being 1 mg of Cetirizine per kilogram.
You may be wondering whether Claritin or Zyrtec is the best pet allergy medicine—but which antihistamine works best for you depends on the severity of your symptoms. For example, a person with a mild allergy to cats or dogs may do well with Claritin. Another person with more severe allergies may do better with Zyrtec.
When accidentally ingested by dogs and cats, antihistamine poisoning can result in clinical signs of severe agitation, lethargy, sedation, aggression, abnormal heart rate, abnormal blood pressure, vomiting, diarrhea, inappetance, seizures, respiratory depression, and even death.
If your pet has been exposed to any type of antihistamine or toxic substance, contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 immediately.
Allergies in dogs are different than allergies in people. Histamines cause upper respiratory allergies in people, whereas cytokines (not histamines) cause itchy skin in dogs. For dogs with underlying allergies, antihistamines don't control the cytokines (signaling proteins) that cause inflammation and itch.
The following antihistamines appear safe in dogs (note that Benadryl is no longer sold in Australia as diphenhydramine tablets). These doses have essentially been worked out by trial and error and often scaled down from human doses. Bad stuff: We don't know why, but dog allergies respond very poorly to antihistamines.
DO NOT USE ALLEGRA D IN PETS. Fexofenadine is also available an oral suspension that contains xylitol (NOTE: Xylitol may be toxic in dogs). The human oral suspension is not recommended for use in pets.