Allergic contact hypersensitivity more commonly occurs in humans than in dogs or cats in large part because the coat of most companion animal patients functions as a protective barrier [47]. When allergic contact reactions occur, they tend to limit themselves to those regions of the body that are naturally less haired, such as the ventral abdomen, medial thighs, and the interdigital skin or between footpads [47].
Hairless breeds present additional concerns because their lack of fur coverage puts them at increased risk for skin exposure to and contact with environmental irri-tants. A 2007 study by Kimura demonstrated sensitivi-ties specific to a colony of Mexican Hairless Dogs housed in stainless steel cages [47]. Although these dogs required 8–12 months of sensitization to develop spontaneously occurring contact dermatitis, they did ultimately present with macroscopic lesions that included macules and papules [47].
As exposure to the inciting agent persisted, inflamma-tory dermatitis developed and progressed [47]. Chronic lesions included lichenification and hyperpigmentation [47]. In addition, the skin became dry and scaly. Some patients also developed skin fissures [47].
Patients clinically improved when they were relocated from stainless steel housing to concrete flooring with concrete and wooden resting areas [47].
Follow‐up patch testing of affected patients with metal salts confirmed underlying sensitivity to the constituents of stainless steel cages, including chromium [47].
Chromium has been reported in the human medical lit-erature as a cause of occupational dermatitis [48–58].
Human males appear to be predisposed [47]. Likewise, male hairless dogs appear more likely to develop allergic contact hypersensitivity [47].
The implications of these findings are that the housing of hairless breeds must be considered in light of their (a) (b) Figure 9.7 (a) Severe Malassezia dermatitis in a canine patient.
Note the extensive lichenification and hyperpigmentation of the ventral abdomen. Source: Courtesy of Dr. Elizabeth Robbins. (b) Same patient as depicted in Figure 9.7a, following two months of medical treatment. Note the improvement in the skin: the lichenification has resolved‚ and the skin has resumed its normal shade of pink. Source: Courtesy of Dr. Elizabeth Robbins.
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