A contact allergy of the skin – known as contact dermatitis, is triggered by an overreaction of the immune system. After contact with the allergen, inflammatory cells migrate into the affected area, and release certain components which cause the classical symptoms of an allergic reaction. As opposed to atopia, a contact dermatitis reaction is usually limited to a confined area of skin, and has the potential to heal completely.
The symptoms of a contact dermatitis vary. Often, an intense reddening and swelling of the skin is develops quickly, usually in combination with an itching sensation. Affected skin may also show whales (round circumscribed swellings of the skin, which may be reddened at the surface) and pustules (small, pus-filled bubbles). In rare cases, the coat hair on the irritated skin is falls out and leaves a bald spot. Common areas of affection are the groin, chest, under-belly or the nose, as these body parts are often the first to make contact with a potentially harmful agent. Symptoms of a contact dermatitis usually wane within a short period of time, provided no renewed contact with the allergen is made. In the case of pollen or other plant-associated particles, periodic episodes may occur, which can be linked to seasons or certain locations.
The offending agent causing contact dermatitis may have made direct contact with the skin of the animal. Usual dermatitis causing agents include paint, varnish, wheat and wheat-related products, plant particles, detergents and others. Alternatively, other offending agents may be causing the dermatitis after having been inhaled. The usual suspects include dust mites, pollen, and others. Because spring and summer are seasons when plant growth primarily occurs, and owners may find their animals at a higher risk for contact dermatitis during these seasons. Also, tendency towards these allergies may be inherited, especially in pure-breeds.
Uncomplicated cases of contact dermatitis are usually short-lived and disappear before long. If symptoms persist for days, or if an extensive area of the skin is affected, examination and treatment are necessary. If the offending agent can be determined and removed through taking the proper measure, allergic reactions may be relieved permanently. Depending on what is causing the contact dermatitis, such countermeasures may include, diet change, supplying a new sleeping box, flea eradication, an other measures taken in order to prevent the offending agent from coming in contact with the animal. If the allergy is season-dependant, medical treatment with anti-allergic drugs is often necessary during sensitive periods. In rare cases, prolonged contact with an allergen may trigger a pronounced sensitivity towards allergens. See our section on atopy for more information, and includes a larger number of additional allergens that require permanent treatment.
If the symptoms of a contact dermatitis do not regress after a couple of days, or in very severe cases of contact dermatitis, you should consult a vet. Mild skin irritations, or irritations that occur over a defined and limited area can be washed with lukewarm water or salty chamomile tea, which can ease the itching-sensation. Very small lesions can be covered with a curd and then wrapped with a light bandage.