12 January 2021

Allergic Dermatitis

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Cate Brothwell, Vet

Allergic dermatitis is a common condition in dogs where the skin becomes inflamed and itchy (pruritic). The condition also affects cats but is less common.

Atopy results from exposure to a variety of environmental allergens such as pollens, human and animal dander (dead skin) and storage mites. The allergens reach the skin through direct contact or are inhaled and absorbed into the blood and transferred to the skin. In atopic individuals inflammation and itching of the face, ears, feet, and underside of the chest and abdomen is common.

The allergy may be seasonal or present all year round depending on which allergens are involved. Most animals with atopy are allergic to more than one allergen.

Other common allergens include parasites, especially fleas, and food which can complicate atopy.

Control of Atopy

Atopy can not be cured so must be effectively managed throughout life to prevent suffering. Management includes:

  1. Control of exposure to allergens
  2. Therapy directed at controlling the inflammation and itching
  3. Therapy to control ‘flare factors’ such as bacteria, yeasts and parasites

1. Avoiding Exposure to Allergens

Completely avoiding allergens, except in the case of flea and food allergy, is nearly impossible but we can reduce exposure to certain environmental allergens.

  • Put your dog outside while dusting and vacuuming. Avoid vacuum cleaners with bags as these tend to produce dust aerosols.
  • Use a damp duster to clean to avoid producing aerosols of dust.
  • Avoid carpets especially where your dog sleeps as they contain huge numbers of dust mites.
  • Wash your pet’s bed weekly and do not allow them to sleep in your bedroom or bed, as this is where the highest dust mite concentrations will be in the home.
  • Avoid the use of perfumed sprays, aerosols and air fresheners.
  • Prevent access to freshly cut grass if your dog’s skin is sensitive. Wiping your dog’s feet when they come in from a walk can help to remove allergens.
  • Avoid having flowers, plants in the house as they will increase the numbers of airborne pollens.
  • Regularly shampooing your dog physically removes allergens from the coat and reduces skin contact.

2. Therapy to control Inflammation and Itching


This involves identifying allergens through a blood test and having a specific vaccine made directed towards these allergens. The vaccine is given regularly to dampen down the allergic reaction, often for life. This can be effective in up to 70% of cases, though doesn’t offer a cure and takes a while before a positive effect is seen. The most appropriate individuals for immunotherapy are young dogs with a fairly short history of skin disease, not where the problem has been present for a long period of time.


These drugs work quickly and are very effective in controlling itching but should be avoided for long term use as they have some harmful side effects. Giving the medication at reduced doses or every other day can help. These can also be used topically as sprays or gels if we are treating a specific area.


This is a fairly new therapy that quickly helps to control itching by blocking the itch nerve pathway. There are few side effects and the medication can be very effective. It is a tablet that is given daily.


This is the most up to date medication available and is reported to be extremely safe and effective. It is given monthly by injection and works quickly by blocking the itch pathway. It will not interact with other medications.


This medication modifies the immune reaction involved in allergy development and takes a few weeks for an effect to be seen. The most common side effects are vomiting and diarrhoea, but these can be reduced by administering the tablets with food.


These are not licensed for use in dogs and cats but are quite often used alongside other therapies to control itching. They are not particularly effective on their own for most individuals but can help to reduce doses of other medications required.

Essential Fatty Acid (eFA) Supplementation

These are available as capsules, pumps and pipettes and can be administered orally or topically. eFAs can help to improve the defense barrier mechanism of the skin and should ideally be given regularly to all atopic cats and dogs.

3. Controlling ‘Flare Factors’-Bacteria, yeasts and Parasites

Shampoos and Topical Skin Care

Medicated shampoos are helpful in eliminating and controlling secondary infections from Staphylococcal bacteria and Malassezia yeasts. These organisms usually live as commensals within the skin, but in some individuals numbers may increase resulting in infection (pyoderma). This will increase irritation and itching.

Systemic Therapy for Secondary Infection

Sometimes antibiotics may be required to control secondary infections in severe cases. These may be a periodic requirement for some individuals.

Flea Control

Flea bite hypersensitivity is very common in both dogs and cats, so effective flea control is of paramount importance. This should include regularly treating all the pets within the household with a prescription product and treating the environment with a household spray. Monthly prescription parasite treatment is included in our Complete Care Club.

It is recommended that the following approach be adopted for all animals with allergic dermatitis where possible:

  • Try to reduce exposure to both indoor and outdoor allergens.
  • Use one or more prescribed therapies to control the itching when necessary.
  • Regularly shampoo the skin to control secondary infection using an appropriate shampoo (as directed by your vet).
  • Give a ‘hypoallergenic’ diet (selected protein or hydrolysed protein) to manage food allergy and to control itching in more complex cases where more than one allergen is involved.
  • Give essential fatty acid supplements to improve the barrier mechanism of the skin.
  • Use regular, prescription flea control.

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