] 18 An Introduction to Medical Mycology 



also that with the dermatophytid described by Williams there was a ten- 

 dency to a localized rash, the sides of the fingers and the palms usually 

 being the sites. The reason for this localization is not known. The terminal 

 circulation of the hands, traumatic factors, contact with fungi producing 

 local sensitization and sensitization to light have been considered. It is not 

 by any means a unique experience in dermatology to be unable to explain 

 localization of a disease process. No one has satisfactorily explained the 

 frequent involvement of the knees and elbows in psoriasis. In the classic 

 dermatophytid following a deep infection of hair follicles, the trunk was 

 usually involved. In this latter instance the character of the rash varied 

 considerably. Follicular localization of lichenoid papules was common, 

 but eruptions simulating erythema toxicum were also observed. In the 

 type described by Williams, the lesions are essentially vesicular, being 

 similar in appearance to dyshidrosis, although the contents frequently 

 become purulent. Constitutional symptoms, often associated with der- 

 matophytids secondary to kerion, are not commonly part of the syndrome 

 which includes a rash secondary to tinea pedis. 



The term dermatophytid (or trichophytid ) appears to have been con- 

 siderably overworked in this country. It is used by many without any tan- 

 gible evidence of proof to account for the erythematous, vesicular and 

 eczematous eruptions which so commonly affect the hands. We believe 

 that a diagnosis of dermatophytid should be arrived at only after careful 

 observation and study. There are definite criteria which must be fulfilled 

 before this diagnosis is acceptable. Peck has laid down theoretically sound 

 rules. His dictum that a positive blood culture is essential is perhaps too 

 drastic. The following conditions for the diagnosis of dermatophytid, how- 

 ever, are minimal and also obligatory. 



1. There must be a demonstrable focus, and this focus must contain 

 pathogenic fungi. On the feet, in the majority of instances, the causative 

 fungus is T. gypseum. We have never observed dermatophytid with T. 

 purpureum. 



2. The secondary rash may be due to irritation of the primary focus 

 by treatment or to a spontaneous inflammatory change. 



3. The intracutaneous test with trichophytin reveals a positive reaction at 

 the test site. 



4. Fungi are usually not found in the lesions of dermatophytid. 



5. The rash disappears spontaneously when the focus has been eradi- 

 cated. The only exceptions occur when there are secondary eczematous 

 changes and the rash continues because of sensitivity to other substances 

 or because of the action of primary irritants. 



In all cases, even if the appearance of the rash and the results of the 



