2206 



THE DERMATOZOIASES 



Diagnosis. — The characteristic features of seasonr 1 bullous 

 dermatitis are as follows: — 



1. The sudden appearance of bullae, varying in size and number, 

 surrounded by a certain amount of inflammatory redness. 



2. The persons in whom the bullae are found are usually in 

 good health, and as a rule they are unable to assign a cause for 

 the eruption. 



3. The bullae are single or grouped together, often in a row. 



4. There is no tendency to bilateral sjrtnmetry. 



5. In a given individual usually only one region of the body is 

 affected. 



6. A number of healthy people living in the same place may be 

 similarly affected at the same time. 



7. The bullae only appear during a certain season of the year. 

 The differential diagnosis requires to be made from the following 



accidents and diseases causing bullae : — 



1. Seasonal bullous dermatitis may be readily separated from 

 the bullae caused by burns and scalds, and by chemicals, by the 

 history of the case. 



2. It has also to be differentiated from the various forms of 

 Hydroa as follows: — 



[a) It can be separated from the milder forms of dermatitis 

 herpetiformis by the absence of severe itching and of circinate and 

 papular erythematous lesions, and by the absence of the tendency 

 of the bullae to be grouped like herpes. 



[h) From the rare form of dermatitis herpetiformis called hydroa 

 pruriginosa it can be diagnosed by the larger size of its bullae, 

 which do not appear in successive crops. 



(c) From dermatitis recurrens it can be distinguished from the 

 hiemal variety by only appearing in warm weather, and from the 

 aestival in not being papulo-vesicular in character. 



3. It may be difierentiated from herpes zoster by the absence 

 of severe pain, lasting for three to four days before the appearance of 

 the eruption, and by the non-distribution of the bullae in Head's areas. 



4. From Acute Pemphigus it is easily separated by the absence 

 of the severe constitutional symptoms. 



5. It can be recognized as distinct from dermatitis venenata, 

 due to plants, by the absence of the marked oedema and erythema, 

 which generally attack the face, hands, and genitalia, and by the 

 presence of bullae. 



6. It is easily separable from Dermatitis caused by mites, as 

 these give rise to small wheals and vesicles, and not to bullae. 



7. Ant and tick bites, stings of wasps, bees, scorpions, centipedes, 

 etc., are at once differentiated because the eruption in Ihe present 

 instance is bullous. 



As the eruptions described by Rodhain and Houssiau and by Ross 

 are stated to be vesicular, it is possible that these may be differen- 

 tiated clinically from this bullous type, while it certainly is not 

 so severe as the eruption describe d by P. Da Silva, in that ulcera- 



