1910] Pediculoides Noxious to Man 35 



The lesion which is typical of the disease is the urticaria vesi- 

 culosa. The urticarial , lesion varies in size from that of a 

 split pea to that of a penny; it is surrounded by a pinkish halo, 

 varying in intensity of color from a pale pink to a most bright 

 pink. The "hive" like lesion is at first blanched, but later 

 becomes a rose red color. It is elevated about i or 2 mm. above 

 the skin surface, and is surmounted by a small vesicle containing 

 a whitish fluid marking the place of' inoculation. The vesicle 

 is about I or 2 mm. in diameter and elevated about 3 mm. above 

 the surface of the urticarial lesion. As the lesion grows old it 

 goes through the process of evolution : (i) it is blanched and has 

 a central vesicle; (2) it is rose red and the vesicle may become a 

 pustule; (3) it generally recedes to the skin level with scab for- 

 mation, due to the scratching; (4) it leaves a browinsh or green- 

 ish-yellow or purple spot on the skin surface. In debilitated 

 patients the markings look not unlike faded indelible pencil 

 marks. (This was noted in a patient suffering from pulmonary 

 tuberculosis.) These discolorations may last for several weeks. 



The anatomical location of the lesions is generally the back, 

 sides and abdomen, and less frequently the arms and legs. The 

 neck has very few lesions; the face, hands and feet have very 

 few or none. 



The number of lesions depends upon the number of mites, 

 ranging in number from very few to thousands ; in some cases the 

 back and abdomen have been almost a solid mass of lesions — 

 new lesions on the tops of old lesions, so having lesions in all 

 stages of development. 



Obscurity Surrounding the Occurrence of the 



Dermatitis. 



The exact nature of this eruptive disease was not at all under- 

 stood by the medical profession throughout the country. In 

 South-western Virginia, threshermen suffered from the same dis- 

 order, but attributed it to- "chiggers," and local physicians, 

 though skeptical, were themselves unable to correctly diagnosis 

 or to account for the trouble. As the disease is not serious and 

 passes away in the course of time without leaving the patient in 

 any way permanently injured, it seems to have been passed over 

 by medical men without investigation excepting by the physi- 

 cians w^hose publications have just been cited. Among the people 

 themselves the eruption was probably more frequently attributed 



