470 NON-PARASITIC SKIN DISEASES 



hair. Under these crusts infection flourishes and decora- 

 position occurs, further irritating the skin. 



Etiology. Various irritants which produce dermatitis 

 may be the remote causes of eczema. The most frequent 

 external cause is the accumulation of dirt on the skin, 

 especially when the hair is long. Consequently the regions 

 most commonly affected are the root of the tail, along the 

 back, shoulders, neck and back of the ears. It is more 

 common in long-haired dogs. Digestive disturbance has 

 an indirect relation to eczema. Decomposing food is a 

 common cause, as is overfeeding. Probably the most 

 persisting forms of eczema occur in overfed, fat animals. 



Pathology . The skin may show all the stages of inflam- 

 mation from acute to chronic. As it is a chronic condition, 

 the acute symptoms are usually induced by scratching or 

 biting the parts. 



Symptoms. The early stages appear as an ordinary 

 dermatitis progressing through the various stages of inflam- 

 mation until the pustular eruptions occur. Recovery may 

 occur spontaneously at this time, or with proper treatment, 

 but if not it passes on to the eczematous stage. Pustules 

 continue to form and discharge their contents often unno- 

 ticed, under the long hair and crusts. If sufficient to keep 

 the skin moist it is commonly classed as weeping eczema. 

 The itching is intense, and the frequent scratching, biting 

 or rubbing removes the matted hair and crusts leaving a 

 raw bleeding surface. The skin lesions may occur in one or 

 more small areas or over a gradually increasing large surface. 

 In consequence of continued efforts to relieve the itching by 

 licking and scratching, the inflammation extends into the 

 deeper layers of the skin. Healing occurs in three or four 

 weeks with recurrence of the condition. The skin becomes 

 thickened and fissured, and bleeds easily. Scales continue 

 to form on these partly healed areas. Some of the hair bulbs 

 atrophy or are destroyed and only a partial growth of hair 

 reappears on the surface. A recurrence of the condition each 

 succeeding summer is quite common in well fed house pets 

 especially among well bred dogs with fine skins, as the 

 poodle. 



