CHAPTER XIX 

 IRRITANTS AND COUNTERIRRITANTS 



lEEiTAiifTS are agents which cause hyperemia and inflammation 

 when applied to the surface of the body. When applied for the relief 

 of disease in remote 'parts of the body they are called counter irritants, 



Counterirritation or irritation of the skin for internal diseases, 

 is a practice which dates back to the earliest days of medicine. The 

 theories upon which the practice is based have changed very fre- 

 quently to meet the advances in medical science. In the early days 

 when disease was considered as an entity, or humor, the theory of 

 revulsion or derivation was much in vogue. The purpose of the irri- 

 tation of the skin was to draw the disease from the deeper portions 

 to the skin. Then it was held that if fluid was dravsni to the skin, con- 

 gestion of the internal organs would be relieved. This theory has also 

 held more or less even in modem times. It was also noticed very 

 early in medicine that counterirritation often relieved the pain in in- 

 ternal organs. The irritation was obtained in various ways. Many 

 drugs were used, also many mechanical devices, such as burning, elec- 

 tricity, or setons or rowels introduced. The last two named agents 

 not only served as irritants but also supplied a means of exit for the 

 humor. Most of these theories are interesting only from a historical 

 standpoint, but counterirritation is still used for the relief of pain of 

 internal organs, and to produce a change in the distribution of blood. 



These agents may be classified into three groups according to the 

 intensity of their action. If they simply produce redness under 

 ordinary conditions they are termed ruhifacients. If the action is 

 more intense and blisters are formed, they are termed vesicants, 

 while if they produce pustulation in the necks of the glands, they are 

 termed pustulants. 



Action. The action of these agents may be described as local 

 and remote. 



Local action. This is evidenced by a feeling of warmth to the 

 part, burning or pain ; the skin becomes reddened, congested and sen- 

 sitive. These symptoms last for some time and recede gradually. 

 Some desquamation may follow if the irritant has been applied for 

 some time. If a stronger irritant is used, the same symptoms as de- 

 scribed above will occur, but will be followed by small vesicles under 

 the epidermis. These may coalesce so that a large vesicle or blister 



is formed. Upon removal of the vesicant, the fluid is slowly ab- 



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