Dog Allergies – Causes & Symptoms

What Are The Types Of Allergies in Dogs

Dog with allergies scratching

Generally, in dogs, allergies are classed into three main categories.

  • Reaction To Inhaled Allergens (Canine Atopy)
  • Reaction To Insect Bites (Flea Allergy Dermatitis)
  • Reaction To Food (Food Allergy) And Drugs
  • Contact Allergic Dermatitis – this is uncommon



Reaction To Inhaled Allergens (Canine Atopy)

Atopy means allergic hypersensitivity. Canine atopy is often called atopic dermatitis.

Common inhaled allergens include pollen, molds, dust and dust mites.

Reaction To Insect Bites (Flea Allergy Dermatitis)

The most common insect bites on dogs are flea bites. When an insect bites any animal, it injects saliva into the bite wound. There are many different components in the saliva, and a dog may be allergic to one or more. If a dog is sensitive to flea bites, a single flea bite can cause an allergic reaction.

Reaction To Food (Food Allergy) And Drugs

In most dogs, the reaction to consuming a food that they are allergic to is itchy skin not vomiting. If a food makes a dog vomit and/or have diarrhea then it is considered food intolerance and not an allergic reaction.

The most common food allergies are milk and milk products, grains, eggs, fish and meats. The most common grains that can trigger an allergic response are corn, wheat and soy. The most common meats are beef, chicken and lamb.

Contact Allergic Dermatitis

Contact allergic dermatitis is quite rare in dogs.

As the name suggests this allergy is caused by substance that come into contact with the outside of the dog. It is different from irritant dermatitis, such as a reaction to irritating chemicals, which will occur in every dog.

Examples of things that can cause contact allergic dermatitis are carpet deodorizers, dyes, rubber, wool and nickel.

What Are The Potential Symptoms Of Canine Allergies

Though allergies can be due to a range of different causes, most allergic reactions will have the similar symptoms in dogs, mainly affecting their skin.

Itchy skin, rubbing and licking paws

Once a dog’s skin has begun to become sensitive to an allergen, they will start to react to the itch. Dogs will scratch various parts of their bodies with tier paws; rub their head, in particular the muzzle, on furniture, carpet, grass etc; and often start to lick and/or chew their paws.

Secondary effects of itchy skin

If a dog is frequently scratching and chewing, there will start to be secondary effects. There may be loss of hair in patches, areas of skin may start to get red or scaly, or look dry, and there may be raw areas. Frequently these areas will become infected.

In contact allergic dermatitis there may be small blisters or red bumps. Occasionally a dog may get hives (urticaria, which are small bumps in the skin). Insect bites are the most frequent cause of hives. They will often cause the hair in that area to stand up.

In some dogs the constant licking of an area, particularly a joint, can lead to a lick granuloma. These are very hard to treat (see the section on lick granulomas for more information about what they look like and potential treatments).

Ear infections

Allergies will affect many dogs’ ears, causing the ears to become irritated and resulting in an overproduction of wax. The excess wax along with the trapped dead skin and dirt can provide an environment for the overgrowth of bacteria and yeast in the ear. This leads to problems with recurrent ear infections.


In a few dogs, an allergic response can lead to angioedema, which is a rapid swelling. In dogs, when angioedema is due to an allergic reaction (there are other diseases that can also cause angioedema), it usually occurs in the face, most frequently the muzzle and round the eyes. A dog may not be open their eyes. Usually the angioedema will start to go away after a while. If the angioedema starts to make it difficult for your dog to breathe seek veterinary help immediately. Also, if the angioedema does not recede, see you vet for treatment.

Irritated eyes

Some dogs may get mild conjunctivitis (red eye or pink eye). This is irritation of the conjunctival membrane of the eye.

Anaphylactic Shock

Anaphylaxis is an extreme, life threatening allergic reaction.

Symptoms can include agitation, difficulty breathing, harsh breathing sounds, limbs may feel cold, vomiting, diarrhea, weakness, pale gums, followed by coma and death if untreated. Anaphylactic shock can start with itching, or it may come on immediately.

If you think your dog might be going into anaphylactic shock, seek veterinary treatment immediately. Without rapidly receiving epinephrine, oxygen and other treatments, a dog in anaphylactic shock will quickly die.

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