Typical allergens causing atopic dermatitis include house dust mites, pollens, mould spores and occasionally foods. Many dogs have multiple allergies and may even suffer from a combination of atopic dermatitis and other hypersensitivities, most notably flea allergy.

Each dog may have an allergic threshold. When the level of allergen exposure is below this threshold, there are no clinical signs. Once this threshold has been exceeded, pruritus and skin lesions develop. Any additional factors that cause skin inflammation, such as the presence of fleas or a microbial infection, may contribute to the development of clinical signs. These are known as ‘flare factors’.

Any breed of dog may be affected but some are more prone than others. The breed incidence varies geographically as genetic factors contribute to the susceptibility of certain breeds to develop atopic dermatitis.

Some of the breeds most commonly reported to be affected by atopic dermatitis include:

• Terriers, especially West Highland White Terriers and Staffordshire Bull Terriers
• Boxers
• Labrador Retrievers, Golden Retrievers
• German Shepherds