152 BACTERIOLOGY FOR NURSES 



is attacked, with the result that there is an excess of liberated poi- 

 son which gives rise to the anaphylactic reaction. If the dose of 

 serum has been small or if a second injection follows the first in 

 less than six to eight days there is seldom any reaction. If, how- 

 ever, a second injection is made a few months after the first an 

 immediate reaction often follows. If a year or more elapse 

 between the injections there is usually no danger of a reaction. 

 By that time the antibody has disappeared from the circula- 

 tion. The rare fatal cases so far reported have followed first 

 injections, presumably because the individuals were already 

 hypersensitive. 



Anaphylactic or allergic skin reactions are frequently employed 

 as an aid in diagnosis. For instance, when tubercle protein (tuber- 

 culein), syphilis protein (leutin), glanders protein (mallein), etc., 

 is applied or injected into the skin of an individual sensitized to 

 that particular protein a local reaction occurs characterized by 

 congestion and edema. If, for example, tuberculein be rubbed 

 into the skin of a normal individual he will not react because he 

 has not been sensitized, whereas a tuberculous patient, except one 

 in the last stage, reacts promptly. The difference between the 

 normal individual and the one in the final stage of tuberculosis 

 is that the former has not been sensitized while the latter has 

 had his anaphylactic powers exhausted ; consequently he presents 

 little or no resistance against the advance of the infection. 



The so-called food idiosyncrasies are also instances of anaphy- 

 laxis. The articles of diet usually responsible are fish, tomatoes, 

 strawberries, pork, eggs, etc. ; the symptoms produced are skin 

 eruptions, gastro-intestinal disorders, and vaso-motor disturbances. 

 When there is a difficulty in determining which food is responsible 

 the skin test may be employed by rubbing a drop of the food itself 

 or a watery extract into a scratch upon the skin. The reaction 

 comes on within thirty minutes and is demonstrated by a pink 

 red edematous area. 



The Shick skin test should be distinguished from the above. 

 It is not an allergic skin reaction, it depends upon an entirely 

 different principle. 



