Avoiding disaster dermatology cases (Proceedings)

The allergic patient can present with myriad symptoms, all related to the underlying cause. As is the case with atopic dermatitis, the symptoms manifested result from an "overproduction" of allergen specific IgE to environmental allergens. Cutaneous adverse reactions to food (ARF) are a result of either "true" food allergy related to the overproduction of food allergen specific IgE, or a food intolerance which is not a true immunologic reaction. Patients with flea allergic dermatitis produce excess IgE in response to flea saliva and display clinical signs somewhat distinctive to the syndrome. However, overlap can occur between the 3 allergic syndromes and it is not uncommon to encounter a patient that suffers from both atopic dermatitis and adverse reactions to food that also experiences a seasonal flare consistent with exposure to fleas. The symptoms that are typically reported by the owner that are attributed to the previously diagnosed allergic diseases are then that much more intense and often are much more controllable with the institution of appropriate flea control measures. Thus recognizing, addressing and managing the threshold effect of pruritus stimulators is key to success.

Allergy Scenarios:

The patient with unilateral otitis.

Differential diagnoses for this patient include a foreign body, neoplasia, hypothyroidism and ARF. Once the foreign body or neoplasia can be eliminated, either an elimination diet trial and/or thyroid testing are performed based upon additional clinical signs that may be present. Consider delaying thyroid testing if the patient has received oral or topical corticosteroid therapy for the otitis. Resolution of the secondary yeast and/or bacterial infections must occur in order to interpret the results.

The patient with recurrent otitis.

Differential diagnoses for this patient include allergic disease (atopy or ARF) or endocrinopathies based upon additional clinical signs. Again, the secondary infections must be resolved in order to further identify the underlying cause. Allergic otitis without secondary infections does occur and can be managed by addressing the underlying cause or with mild topical corticosteroids, such as hydrocortisone containing otics.

The patient with intense non-seasonal pruritus.

Differential diagnoses include CARF and scabies infestation. Secondary infections (especially Malassezia spp.) must be treated and resolved prior to considering the pruritus intense and non-seasonal. Look for GI symptoms as well, such as frequent bowel movements (> 2 per day), borborygmus, vomiting, frequent grass-eating behavior, poor appetite, etc. Always eliminate scabies as a differential diagnosis with either an ivermectin or selamectin trial (every 2 weeks for 3 treatments, thus total of 2 life cycles) or use weekly lime sulfur dips to treat the pruritus as well as rule out scabies as a cause for the pruritus (6 weekly dips will satisfy the 2 life cycles requirement).

Novel protein diets are currently the most reliable method (other than home cooking) based on recent data. Some patients will continue to fail hydrolyzed diet trials based on pruritus alone, although the lesions (erythema, lichenification, etc.) may appear improved.

The patient with mild seasonal pedal or facial pruritus.

This patient is the poster child of atopy and can benefit from either seasonal administration of corticosteroids (when used judiciously), management with fatty acids and/or antihistamines, or hyposensitization. The younger more mildly affected patient often benefits from hyposensitization alone rather than the older, more severely affected patient that will typically require therapy in addition to hyposensitization. Most atopics peak in reference to the severity of symptoms by the age of 6 years, however the effects of chronic secondary infections as well as corticosteroid excess can make these symptoms appear to worsen with age.

Crucial to the management of an atopic patient is avoidance as well as management of secondary infections. The main route of exposure is now thought to be via percutaneous exposure rather than inhalation, thus wiping the feet after a trip outside can be very helpful in decreasing exposure. Shampooing not only hydrates the skin and can address any secondary infections present, but it also removes pollens and mold allergens from the hair coat and skin, thus further decreasing exposure. House dust mite impermeable box spring, mattress and pillow covers are also essential in the patient that displays more perennial symptoms.