Allergic Dermatitis in Dogs

Symptoms

Allergic dermatitis refers to skin inflammation caused by an allergic reaction. Common symptoms include:

• Itching (pruritus) — scratching, biting, or licking (see itch scale)

• Red, inflamed skin — especially on paws, ears, belly, and armpits

• Hair loss — due to excessive scratching and licking OR appears to be thinner for no reason

• Scabs or sores — from self-trauma or secondary infections

• Ear infections — recurring or chronic

• Thickened or darkened skin — in chronic cases

• Hot spots — localized areas of intense inflammation

Types

Atopic Dermatitis (Environmental Allergies)

• Typically things in the environment we cannot avoid (pollen, mold, dust mites, grasses, etc.)

• Many start seasonally or wax and wane throughout the year, some are year-round (i.e., dust mites)

• Typically they worsen as the dog gets older. What works now may not work forever

Food Allergy Dermatitis

• Caused by proteins in food (e.g., beef, chicken, dairy), NOT grains in most cases!

• Non-seasonal; may be accompanied by digestive issues

• Symptoms can be seen as early as 3 months of age (they have been like this their whole life!)

Flea Allergy Dermatitis (FAD)

• Allergic reaction to flea saliva. Only needs one or two bites to cause a severe reaction!

Contact Dermatitis

• Caused by direct contact with irritants (e.g., chemicals, plants, shampoos)

• Localized to areas of contact

Treatments

Goal: Stop the underlying inappropriate immune system response causing itch, inflammation, and damage to the skin barrier.

1. Avoidance of Allergens

• Flea prevention (monthly treatments): Recommended for all dogs and strongly recommended for all cats as an initial therapy

• Hypoallergenic diets or novel protein diets: Need 8-12 weeks with NO CHEATING for the system to settle down (toddlers, grandmas with dementia), cat food, or treats that are not hypoallergenic. The "diagnosis is in the challenge" — we need to feed the old food back and observe an increase in itch to confirm

2. Medications

• Antihistamines (Cetirizine) ($): Reduce mild symptoms, typically not effective later

• Corticosteroids (Prednisone) ($): Cheap, effective, risk of side effects with long-term use

• Oclacitinib (Apoquel) ($$): Receptor interference — prevents the itch signal from causing itch

• Ilunocitinib (Zenrelia) ($$): Receptor interference — prevents the itch signal from causing itch

• Lokivetmab (Cytopoint) ($$): Injectable monoclonal antibody — destroys itch signal

• Cyclosporine (Atopica) ($$$): Immune suppressant for refractory or specific cases

3. Topical Therapies

• Ear drops / steroid spray ($$): Treat bacterial and yeast infections, local anti-inflammatory

• Medicated shampoos ($): Remove extra grease or crusts — antibacterial, antifungal, anti-itch

• Sprays and creams ($): For localized irritation or contact dermatitis

4. Immunotherapy (Sublingual Allergy Desensitization Drops)

• Custom-made desensitization therapy based on ENVIRONMENTAL ALLERGY TEST results

• Cost: Testing + first round of sublingual drops = $1,000-$1,500 to see if it will work

• Can save money on other medications over a patient's life but may need to be combined with other therapy (steroids, Apoquel, Cytopoint) for control

5. Management of Secondary Infections

• Long-term medications DO NOT WORK when an infection is going on. We need to treat both

• Just treating the infection may make symptoms seem better in the short term, but episodes will reoccur until the underlying cause is treated