PRURITUS 257 



Ioss_ of hair is often only temporary, the denuded skin soon 

 again becoming covered with fine downy hair which grows out 

 to full length. Local alopecia appears in the form of small, 

 round bald areas which gradually increase in size and by 

 coalescence form large bald spots. The skin is intact, al- 

 though, as a rule, it is darker in color than normal. 



Diagnosis. — Alopecia might be confused with herpes ton- 

 surans or with mange. However, the absence of scales and 

 broken hair shafts differentiate it from the former; the 

 eczema and presence of the mange mite suffice to distinguish 

 mange from it. 



Treatment. — While general alopecia usually leaves of itself 

 in a few weeks, provided the patient and skin are given good 

 care, the local form is often quite obstinate and frequently 

 incurable. Fluids containing alcohol and some irritant are 

 generally recommended. Tincture of cantharides (1 to 5 

 alcohol), tincture of iodin (1 to 1 to 5 alcohol), and creolin 

 (1 to 10 to 20 alcohol) are examples. 



ERYTHEMA. 



Definition. — Erythema is an inflammatory congestion of 

 the skin which may be primary and result from various 

 mechanical, chemical, and thermic causes; it may be a symp- 

 tom of eczema, or it occurs secondary to infections and intoxi- 

 cations. In hog cholera, erythema is occasionally seen; in 

 swine erysipelas it is a constant symptom. White swine and 

 sheep are affected by it if they eat growing buckwheat in the 

 bright sunlight. 



PRURITUS. 



Definition. — By pruritus an itching of the skin without 

 visible lesion is meant. It may be local or general. 



Etiology. — The causes are not well understood. In some of 

 the infectious diseases, such as rabies, dourine, and in dis- 

 orders due to worms like trichinosis and grub-in-the-head of 

 sheep, it has been observed. Severe general diseases are some- 

 times accompanied by pruritus, such as chronic nephritis, 

 icterus, and diabetes mellitis. 

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