DISEASES OF SKIN 



REDDENING OF SKIN (ERYTHEMA) 



Definition. — By the term " erythema " is meant a simple red- 

 dening of the skin due to the overfilling of the capillary blood- 

 vessels in the deeper layers of the skin. It is not accompanied by 

 any actual change in tissue structure, and is, in reahty, the first 

 step in the production of an inflammation of the skin. The con- 

 dition occurs with sufficient frequency as a simple disease without 

 being followed by tissue changes to deserve separate mention. 



Causes. — Erythema may occur as the result of the application 

 of irritating substances to the skin, such as strong bhstering lini- 

 ments. Thermal irritation is also a frequent cause for erythema, as 

 from frost-bites, the rays of the sun, scalding, or burning. Ery- 

 thema may also result from injuries to the skin, as, for instance, the 

 irritation produced by crawling through or under a board fence. 

 Bites and stings of wasps, bees, and other poisonous insects may 

 cause a simple erythema. 



Erythema is seen as an almost constant lesion in hog-cholera 

 and also in swine erysipeals. In hog-cholera the erythema is often 

 very marked and causes a reddening of almost the entire skin. It 

 is especially noticeable on the skin of the ears, the flanks, the belly, 

 and under the neck. Erythema may frequently be seen as a symp- 

 tom of acute indigestion or after feeding upon spoiled fodder, dis- 

 tillers' mash, and other foods which have an irritating effect upon 

 the skin. In these cases the reddening of the skin is due to the 

 absorption of a poisonous substance from the bowels which es- 

 pecially affects the smaller blood-vessels. 



Symptoms. — The characteristic symptom of the disease is a 

 diffuse redness of the skin. The disease is much more easily de- 

 tected in white hogs, but may be hard to make out in black animals, 

 except in certain parts of the body where the skin is very thin. 

 It is typical of the redness of erythema that if the reddened areas 



