What to Know About Antihistamines for Cats

Medically Reviewed by Amy Flowers, DVM on October 29, 2022
5 min read

Have you ever wondered if Benadryl for cats exists? Perhaps you’ve noticed that your cat has developed sneezing or is itching more than usual.  

Humans aren’t the only ones who end up with runny and stuffy noses, annoying itching, and other allergy symptoms. Pets can end up with these symptoms, too. One common pet known for getting allergies is the cat. 

Animals can develop allergies to just about anything, much like humans can. They can be allergic to flea bites, certain foods, and even allergens in the air.

Like humans, cats can be treated with pet-friendly antihistamines.

Symptoms of allergies in cats can vary depending on the type of allergy your cat is experiencing. 

Flea Allergies. Flea allergies can appear at any time in your cat’s life and occurs when a cat becomes allergic to flea saliva. If your cat is allergic to fleas, it may develop the following symptoms: 

  • Extreme itching 
  • Rashes upon flea bites, typically around the head, neck, tummy, rear legs, and lower back 
  • Excessive grooming habits 
  • Loss of fur (alopecia)
  • Eosinophilic dermatitis, or skin disease caused by parasites, often accompanied by skin lesions 
  • Fleas and flea dirt

Flea allergies that aren’t treated can affect the quality of your cat’s life. 

Food Allergies. When food allergies and their symptoms develop, they typically go unnoticed for months or even years. There is no known cause of food allergies in cats, and they can develop even after a cat has been on the same diet for years. 

When you start noticing symptoms, you may see the following: 

  • Excessive scratching
  • Skin lesions 
  • Loss of fur (alopecia) 
  • Coat deterioration 
  • Vomiting
  • Diarrhea
  • Food avoidance 

These symptoms usually occur gradually and eventually become more intense. Your cat must receive prompt veterinary care when you start noticing these signs. The food allergen must be pinpointed and eliminated from your cat’s diet. 

Environmental Seasonal Allergies. Like you, your cat can develop seasonal and environmental allergies from things like pollen. Symptoms of seasonal allergies include: 

  • Excessive coat or skin clawing or biting 
  • Skin that becomes inflamed, red, or infected 
  • Severe shedding 
  • Chronic ear infections 
  • Respiratory issues, like breathing difficulties, coughing, and wheezing

To diagnose your cat with allergies, your vet will perform a complete physical exam and evaluate your cat’s medical history. Depending on the type of allergy suspected, your veterinarian may perform other tests.

Your veterinarian will examine your cat for signs of fleas and flea dirt to diagnose a flea allergy. They may also perform a skin test. 

When diagnosing a food allergy, things become a little more complicated. The most accurate test to diagnose food allergies is eliminating specific components in your cat’s diet. You’ll have to switch your cat to a food that doesn’t contain the proteins your cat’s diet has previously contained. This trial is lengthy and can take up to 8 to 10 weeks. You may be supplied with a veterinary hydrolyzed protein diet or a veterinary novel protein diet, or you may prepare a novel protein diet at home.

As for seasonal allergies, it can be hard to distinguish them from food and flea allergies, especially since the primary symptom is itchy skin. For this reason, a vet visit must be scheduled as soon as you notice symptoms developing. However, it’s important to note that food allergies can occur year round, flea allergies typically have evidence of fleas, and seasonal allergies occur around the same time every year.

When diagnosing seasonal allergies, your veterinarian will look for patterns in your cat’s symptoms. They will also examine the areas where your cat itches the most. They will look for fleas and flea dirt to rule out flea allergies and ask about your cat’s diet to rule out food allergies. Your veterinarian may also perform a skin test to determine what substance your pet is allergic to.

As with symptoms and diagnoses, treatment for your cat's allergies can also vary. 

For flea allergies, you’ll need to ensure that your cat follows a strict flea control protocol prescribed by your veterinarian. Unfortunately, many of these flea control treatments only kill fleas once the flea has bitten your cat, so your cat may still have a few reactions. In this case, flea repellents are recommended to eliminate fleas. These treatments should be products recommended by your veterinarian. 

Additionally, you’ll need extra care to clean your home as often as possible to help remove fleas and eggs from your carpet and furniture. Steroids and antibiotics may be prescribed to help flare-ups.

Food allergies in cats are treated by avoiding the foods and ingredients that give your cat a reaction. Because food allergies can differ between cats, it’s essential that you work with your veterinarian to come up with a plan to eliminate these ingredients from your cat’s diet. Your veterinarian can prescribe you a specific food or help you choose one that is right for your cat. 

Finally, if seasonal allergies affect your cat, your veterinarian may prescribe or recommend anti-itch sprays, creams, or fatty acid supplements. You may also need to provide your cat with extra at-home care in the form of baths or wiping off their paws to help them avoid allergens. 

Lastly, for allergy flare-ups that come back, pet-friendly antihistamines for cat allergies may be used. 

What Are Pet-Friendly Antihistamines? 

Pet-friendly antihistamines, such as Chlorpheniramine, are anti-allergy medications prescribed to pets with frequent allergy symptoms. These treatments aren’t always effective, and it can take up to 10 days before you notice them helping your cat. Unfortunately, because it can take so long to help, it’s often ineffective in helping with sudden flare-ups. 

Since many antihistamines brands are on the market, it’s vital that you check with your veterinarian before introducing this medication to your pet. 

Benadryl for Cats 

Benadryl is one of the most popular antihistamine medications for people and pets. While it doesn’t have the FDA stamp of approval in use with veterinarian medicine, it is still commonly used to treat allergies in cats and even recommended by many veterinarians. 

It’s easy to access, over-the-counter drug that is safe and effective in treating allergies, but it’s still important to check with your veterinarian before adding Benadryl to your cat’s diet. 

Benadryl will need to be given to your cat in a specific dose. Benadryl for cats dosage is 1 milligram per pound of body weight. 

While Benadryl is typically considered safe, some cats may be more sensitive to this drug and may exhibit the following side effects: 

  • Depression
  • Dry mouth 
  • Foaming at the mouth
  • Vomiting
  • Diarrhea
  • Loss of appetite
  • Urine retention

If you notice any of these symptoms, you may want to consult your veterinarian.