In my experience, immediate adverse reactions to topical shampoos usually are mild and consist of pruritus, erythema, flushing,
and rare urticarial episodes. Many of the patients needing long-term shampoo therapy are patients with pruritic diseases (e.g. atopy). A worsening of the pruritus by the shampoo may be missed or attributed to the underlying disease. I recommend diluting
medicated shampoos before application and triple rinsing afterward. To identify a suitable shampoo in a shampoo-sensitive
dog, perform an open patch test (unlike in the traditional patch test, the test compound in the open patch test is not under
an occlusive bandage). This test involves applying a small amount of diluted shampoo to the dog's abdomen, allowing five minutes
of contact time, and rinsing. Then watch the dog carefully for any signs indicating intolerance (e.g. erythema, pruritus). If the dog shows signs of intolerance, do not use the shampoo.
An interesting question is why the dog in this case tolerated the shampoo previously. Two possible reasons are that allergic
contact reactions can take months to years to develop and that the formulation of the shampoo may have changed.
1. Scott, D.W. et al.: Skin diseases. Muller and Kirk's Small Animal Dermatology, 6th Ed. W.B. Saunders, Philadelphia, Pa., 2001; pp 1125-1183.
2. Holm, K.S. et al.: Eosinophilic dermatitis with edema in nine dogs compared with eosinophilic cellulitis in humans. JAVMA 215 (5):649-653; 1999.
3. Moriello, K.A.: Eosinophilic dermatoses. BSAVA Manual of Small Animal Dermatology, 2nd Ed. (A. Foster; C. Foil, eds.). British Small Animal Veterinary Association, Gloucester, Engl., 2003; pp 233-241.
The photographs and information for this case were provided by Karen A. Moriello, DVM, DACVD, Department of Medical Sciences,
School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.