Allegra, which contains the active ingredient fexofenadine, is a second generation antihistamine. Like Benadryl, it is effective for reducing the symptoms of allergies in dogs, but because it is non-drowsy it is not as effective for treating anxiety or causing sedation. There are several different formulations of Allegra, including a number of combination medicines. Some of these, including Allegra D (which contains pseudoephedrine), should not be given to dogs.

When fexofenadine is given by itself it is considered quite safe.

Recommended Dosage

Note: For safety reasons, never give Allegra to your dog without the approval of your vet, and always follow the vet’s instructions.

Using the plain Allegra formulation which contains fexofenadine as the only active ingredient (check the back of the box for a list of active ingredients), the recommended dosage for dogs is 1 – 2.5 mg/lb. This may be given either once or twice daily depending on your vet’s preference.

The dosage chart and calculator below shows a 1 mg/lb dose.

Chart showing the dosage of fexofenadine for dogs
Dog’s Weight In Pounds: Dosage In Mg:

Allegra products often contain fexofenadine in strengths ranging from 60 mg to 180 mg per pill. Using the tablets instead of the gelcaps is often a good idea, as it is easier to split tablets if needed.

Formulations to Avoid…

Avoid giving your dog the following formulations:

Allegra D: This contains pseudoephedrine which can be dangerous for dogs.

Children’s Oral Suspension (Liquid): This contains xylitol and should not be used.

Because the meltable tablets were designed to work for humans, these may also be inappropriate, but your vet can help you with this.

Example: A 30 lb dog could be given one 60 mg Allegra tablet once or twice daily for a 2 mg/lb dosage.


Is It Safe?

There is currently little information on the safety of fexofenadine for dogs. However, some studies have suggested that the drug is safe and effective for treating allergy-related itching in dogs when compared to methylprednisolone. The drug has also been given to dogs at dosages of up to 2 g/kg without signs of toxicity, and doses of 18 mg/kg are seemingly safe (but this doesn’t mean you should exceed the recommended 1 – 2.5 mg/lb dosage).

It may be unsuitable for dogs who:

  • Are pregnant or nursing.
  • Have poor kidney function/kidney disease.
  • Are hypersensitive to any ingredients in the medicine.


Safety Guidelines

Follow these guidelines to safely treat your dog with Allegra:

  • Do not use unless you have approval and guidance from a vet.
  • Do not use products containing xylitol, pseudoephedrine, or any other substances that are toxic to dogs.
  • Tell the vet about any medical conditions affecting your dog, and any other medicines/supplements you are giving to him.

Although it’s unlikely you are giving your dog fruit juice, it’s important to note that the medicine should not be given with fruit juice.

What Is It Used For?

Allegra may be effective at reducing the symptoms of allergies in dogs. Studies have shown promise for the reduction of itching in dogs with atopic dermatitis.

Side Effects

Based on human reports, the following side effects may be possible:

  • Headaches.
  • Nausea.
  • Painful menstruation.
  • Indigestion.

Even though the medicine is considered non-drowsy, sedation is possible (yet rare), and becomes more common as the dosage increases. Second generation antihistamines may also negatively affect the heart at high doses.


Merck Manuals
Dr. Fiona
Canine and Feline Dermatology Drug Handbook