Allergies causing itchy skin and rashes (allergic dermatitis) are very common in dogs, particularly here in the Bay of Plenty. Allergies can be to airborne allergens such as pollen or mould (atopic dermatitis or atopy); to food; flea bites; or substances that contact the skin such as plants (e.g. Wandering Jew or plastics.)
Atopic dermatitis (atopy) is the most common cause of allergic dermatitis in dogs.
Overview
Atopic dermatitis may affect as much as 10-15% of the dog population, and is extremely common in Tauranga.
It is caused by a reaction to airborne substances in the environment known as ‘allergens’ such as pollen, so is often worse in the season/s where certain pollens or moulds are prevalent (Spring and Summer are often worse). Atopic dermatitis is a lifelong condition that will usually worsen over time. While there is no cure, effective management can control the signs and mean your dog is comfortable and happy. Furthermore, some therapies can help to desensitize your dog to certain allergens, resulting in less skin reaction and clinical signs.
What causes atopic dermatitis?
A genetic component is suspected because certain breeds and families of dogs are predisposed.
The skin of atopic dogs has a defective outer layer (epidermis). When allergens
contact the skin, the immune system creates an inflammatory response, resulting in the signs of itchiness we see in affected dogs. Typical allergens include pollens, molds, dust mites, dander (skin cells) and many other substances.
Conditions often associated with atopy dermatitis:
Ear and skin infections
“Hot spots” (also known as moist dermatitis)
Allergic conjunctivitis — runny or red itchy eyes
Flea allergy dermatitis
Anal gland irritation and scooting
What are the signs?
The most common sign is excessive itchiness, and this can vary in intensity among dogs and can also change over time. The itchiness often has a seasonal component (40-75% of cases) which reflects the allergens involved, but it can progress to becoming a year-round condition.
Dogs react by scratching their body, rubbing on the floor or furniture, licking and chewing their feet, rubbing their faces and scooting. Initially, the skin will appear normal, but over time, there can be hair loss after scratching and licking. Areas of skin where the dog licks or scratches may appear red, and the hair in those spots may have a brown discoloration due to salivary staining.
As the condition progresses, areas of the skin may become darker and thickened.
Secondary infections can appear as rashes on the skin — often on the belly, behind the front legs and around the base of the tail
Which dogs are most commonly affected?
Atopic dogs typically start to show signs between 6-months-old and 3-years-old.
Many breeds of dogs are over-represented, including Labrador Retrievers, Golden Retrievers, Soft-coated Wheaton Terriers, West Highland White Terriers, Jack Russell Terriers, Bulldogs, Boston Terriers, Boxers, Pit Bulls, Shar Peis, Shih Tzus, Weimaraners, and German Shepherds, as well as mixed-breed dogs. At Welcome Bay Vets we see a lot of mixed breed dogs affected by atopy, as well as frequent presentations in pure-bred dogs.
How do we manage an itchy dog?
An itchy dog needs a vet consult. Your vet will take a thorough history examine your dog to work out what diagnostic steps are needed; what is the most likely cause of the itch; whether secondary infections need to be controlled; and then work with you to create a management plan. Remember that we cannot cure allergic dermatitis, so expect ongoing management at home and regular check ups – especially for dogs that have seasonal flares, common with atopic dermatitis.