Section: Veterinary Care In-depth
Diagnosis In-depth
Diagnosis is based on clinical signs, distribution (variable depending on the type of substance involved), resolution of clinical signs with avoidance, and recurrence of clinical signs with re-exposure. Implicating a specific allergen is difficult and requires cooperation with the owner to identify possible sources.
Contact allergy can be differentiated from inhalant allergy (atopy) by the persistence of a primary papular eruption (red bumps) after appropriate antibiotic therapy. In addition, contact allergy completely resolves with confinement whereas atopy does not.
Boarding the animal at the hospital for one to two weeks is recommended to accomplish avoidance. Animals should be shampooed before beginning confinement to remove possible residual material from the skin.
Patch testing can also be used to diagnose contact allergy. Patch testing is difficult and time-consuming but allows identification of the specific substance responsible for clinical signs. The skin on the chest wall is clipped one to two days before the test and potential allergens are applied in close contact with the skin for 48 hours. Thorough bandaging is the best way to achieve contact with the allergen (closed patch test). An open patch test consists of applying the potential allergen to the inner part of the ear and observing the skin for 48 hours.
Specialized devices called Finn chambers may be used to apply the suspected allergen. A positive reaction is indicated by the appearance of edema (soft swelling) and a papular eruption (red bumps) 24 to 48 hours after application of the allergen.
Microscopic pathology. Skin biopsies show inflammation around blood vessels and swelling of cells in the epidermis.
Related Articles
-
1
Atopy in Dogs
Atopic disease (atopy) is a pruritic (itchy) skin disease of animals that is caused by an allergy.
» Read More
-
2
Skin Discharge or Odor in Dogs
Skin odor is a common manifestation of a skin infection; the most common skin infections are bacterial (superficial pyoderma) and yeast (Malassezia dermatitis) infections.
» Read More
-
3
Pruritus (Itchiness) in Dogs
How pruritus affects your dog’s health depends on the degree of the pruritus. Severe pruritus leads to intense scratching, which may result in painful skin lesions that may become infected.
» Read More
-
4
Skin Lesion or Sore in Dogs
There are many different types of skin lesions that can occur in the skin of dogs, and each lesion or combination of lesions can be caused by multiple diseases and conditions.
» Read More
