Uncovering the Triggers: Environmental and Food Allergies

In the last topic in this lesson, we’ll talk about the allergens that often trigger a response in dogs with atopic dermatitis. It’s important to understand that every dog is different. While some dogs will have an allergy to a single allergen, others will be affected by many allergens. And these allergies aren’t static – dogs with atopy are likely to become allergic to more things as they age. According to one UK study, dogs are normally allergic to 5 things (or at least 5 of the things we commonly test for).

House Dust Mites and Storage Mites

Studies have shown that an allergy to house dust mites is the most common type of allergy in dogs, affecting 60-90% of allergic dogs. However, dogs often quickly develop allergies to other types of house mites, including storage mites. Allergies to common storage mites affect 36-80% of allergic dogs, depending on the study.

Feathers and Dander

According to one UK study, the second most common allergen in dogs is to human dander. In other words, dogs are commonly allergic to us, just like we’re allergic to them! Dogs can also be allergic to cats, feathers, and other housemates!


Several studies have shown moulds to be a very common group of allergens. However, this varies regionally, likely due to different moulds in different areas. Allergens to mould occur in 40-60% of allergic dogs.

Plant Pollens

Plant pollen allergies are also very common. Like moulds, plants vary regionally, and therefore the exact plants that dogs react to vary too. It makes it hard to work out which allergens are common. One study compared allergen responses of dogs in London and Edinburgh.

In London, the most common allergens (in approximate order of number of allergic dogs) were:

  • White oak
  • Timothy grass
  • Red Top grass
  • White birch
  • Betula (birch) species
  • English plantain
  • Red clover

As you can see, there are a few tree species included. In Edinburgh, however, dogs were more likely to react to grasses, with these being the most common:

  • Timothy grass
  • Red clover
  • Kentucky blue grass
  • Sweet vernal grass
  • Velvet grass
  • Rye grass
  • Mugwort
  • Dandelion
  • Orchard grass


Malessezia is a species of yeast that normally lives harmlessly on the skin of normal dogs. But some dogs can become hypersensitised to this yeast, meaning they get signs of atopy from contact with it.

Food allergens

There is a lot of debate among vets whether food allergies are related to atopic dermatitis or not. Allergies to food can cause similar symptoms, and the argument was whether this was a different condition that happened to have similar signs, or the same problem. A group of international vet dermatologists have now decided that food allergens can cause atopic dermatitis in some dogs, but that some dogs with food allergies will not get atopic dermatitis and will instead respond with a different set of symptoms.

Flea allergies

Dogs can also be allergic to flea saliva. While fleas are itchy, the itch response an allergic dog gets after being bitten by just one flea is huge. Flea allergy is fairly common in dogs.

Other insects

Allergic reactions to other types of insect are relatively rare in dogs, but biting insects may cause allergies in some isolated cases.

Your Dog’s Triggers

Working out what your dog’s triggers are can be helpful, as you may be able to make adjustments to avoid the allergens. However, this is not the case for all allergens – it can be almost impossible to avoid exposure to certain grass pollens, as hayfever suffers will surely tell you!

We’ll go into a little more detail about how to find out your dog’s triggers – and why it’s not always recommended – in the diagnosis section.


Dogs can be allergic to many different things in the environment, as well as to their food. The most common allergies are to mites and moulds, but plants, insects, and human dander are also common triggers. Finding out your dog’s triggers is sometimes helpful, as you may be able to make lifestyle changes to avoid these triggers.

Key Takeaway

Dogs can be allergic to lots of things, with house dust mites being the most common cause of allergic dermatitis.