570 IMMUNOLOGY 



excitants all seem to lack an antigenic property, it is quite possible 

 that they contain specific haptens and it is conceivable that the 

 newer work on haptens, modified antigens and specificity discussed 

 in previous chapters may lead to a better understanding of the 

 phenomenon of contact dermatitis. 



Physical Factors in Allergy.— Duke (1925, 1932) calls attention 

 lo certain cases of clinical allergy in which the symptoms seem 

 to indicate sensitiveness to heat, cold, or sunlight. He also re- 

 ports cases which he describes as effort sensitiveness. In this 

 connection it is of interest to note that dermographia has long 

 been associated with idiosyncrasy to food, although it is elicited 

 by mechanical streaking of the skin. There is at present a 

 difference of opinion in regard to the "physical allergies." One 

 group of allergists maintains that the symptoms represent a 

 sensitiveness to a physical agent, while another regards the 

 sensitiveness to physical agents as due to physiological disturb- 

 ances associated with hypersensitiveness to organic or inorganic 

 substances. Karady (1939) suggested that a physical stimulus 

 might alter the protein of the blood plasma in such a way as to 

 form an "auto-antigen." Richardson (1940) has been unable 

 to confirm Karady 's work. Attention has also been called to the oc- 

 casional relationship of endocrine dysfunction in skin sensitiveness 

 to physical agents as, for example, the existence of urticaria, ec- 

 zema, etc., in patients suffering from hypothyroidism (Cobb, 1919). 

 For a recent discussion of physical allergy the student is referred 

 to a paper by Swineford (1935). 



Diagnosis of Allergy. — In the diagnosis of clinical allergy a 

 good history is exceedingly important. When the patient is able to 

 keep an accurate and comprehensive diary for a period that in- 

 cludes sevei'al attacks of allergic symptoms, the diagnosis may be- 

 come quite obvious and definitely verifiable by adequate tests. 

 Among the various other devices used by physicians in attempting 

 to ascertain the source of the exciting agent in any particular case 

 of clinical allergy may be mentioned the following: 



a. Elimination Tests.- — Suggestion that the patient avoid cer- 

 tain things that the history incriminates. This is the basis for 

 employing elimination diets in the diagnosis of food allergies. 



