HYPERSENSITIVENESS 565 



ticular i)ollcns to be used in skin tests. Since atmospheric condi- 

 tions such as wind, dust and rain affect the amount of pollen in the 

 air, it is not surprising that the patient associates such conditions 

 with the degree of severity of his symptoms. 



Historical. — The history of hay fever is quite interesting. 

 Duke (1925) states that while cases in which headache, sneezing 

 and itching of the nose were reported during the sixteenth and 

 seventeenth centuries and attributed to the odor of roses, it re- 

 mained for Bostock (1819) to recognize hay fever as a clinical 

 entity. The etiology was not determined until 1856, when Blackley, 

 an English physician, who was subject to seasonal attacks of hay 

 fever and asthma, began his experimental study of the subject and 

 determined that it is caused by pollen. Blackley 's work was not 

 appreciated by clinicians until it was confirmed by Dunbar in 

 1903. The results of Blackley 's extensive investigation may be 

 partially summarized as follows : 



Blackley 's Observations. — 1. He tested, on himself, the pollen 

 from approximately one hundred different species of plants and 

 discovered that while he was sensitive to several, he reacted more 

 severel,v to the pollen of rye tluin to other pollens. 



2. In his experiments he used both dried and fresh preparations 

 and also extracts of pollen. He employed methods involving 

 inhalation, direct application to the mucous meml)rane of the nose, 

 and instillation into the conjunctiva, and was able to produce liay 

 fever symptoms by all of these procedures. 



3. Blackley was the first one to employ skin tests. These he per- 

 formed by rubbing the pollen into a scarified area of the forearm 

 or over the tibia. 



4. He made a quantitative study of the amount of pollen present 

 on different days from early spring until August by exposing, for 

 twenty-four hours, glass slides covered with sticky material and 

 noting the kind and number of pollen grains that adhered to the 

 slide. By comparing these results with his own clinical symptoms 

 he found that the latter increased and decreased in severity as the 

 amount of air-borne pollen to which he was sensitive was large or 

 small. He found that the amount of pollen in the air was affected 

 by atmospheric conditions, being considerably decreased after a 

 heavy rain. In his case there was not sufficient pollen in the air 

 prior to June 8 to cause an attack of hay fever. It is now generally 



