336 



THE POTENCY OF PEPPER TREE POLLEN AS A CAUSE 

 OF HAY FEVER. 



BY 



George Potts, B.Sc, Ph.D. 



Professor of Botany, Grey University College, Bloemfontein. 



Read July 15, 1921. 



Bloemfontein and certain other towns of the drier inland 

 region of South Africa suffer annually in the early summer from 

 a very virulent form of hay fever, which occurs on such a scale 

 as to justify being termed epidemic. A preliminary account (1919) 

 of an investigation into the cause of these epidemics appeared iri 

 Vol. XV of The South African Journal of Science, page 525. 

 It was there stated that the disorder is commonly attributed to 

 the pepper tree (Schinus moUe), a member of the family Anacar- 

 diaceae, and indigenous to South America. This plant is grown 

 as a street tree in nearly all South African towns, but in especially 

 large numbers in many of the towns and villages of the Karroo 

 itself and neighbouring karroid regions. It was shown that this 

 tree has very sticky pollen, that its flowers produce nectar freely 

 and are visited by insects, and that it has in every respect typical 

 insect-pollinated flowers. According to all past experience such 

 a plant therefore should not cause hay fever in nature. 



Since the preliminarv report was written, the investigation 

 has been continued along several lines, including a determination 

 of the pollens floating in the air. The present report is confined 

 to some experiments, designed to test the power of pepper tree 

 pollen to cause the disorder ; but it is hoped to publish the complete 

 results of the investigation at an early date. 



The method adopted in the experiments was what is known 

 as the cutaneous reaction, and consists in scarifying the skin (as 

 in ordinary vaccination) and applying to it the pollen or pollen 

 extract to be tested. In the case of a patient susceptible to the 

 particular pollen used, the result is a local reddening and swelling, 

 the extent of which is proportional to the patient's degree of 

 susceptibility; and if the patient is not susceptible to that par- 

 ticular kind of pollen there is no reaction. The test, which causes 

 little or no inconvenience to the patient, depends upon the fact 

 that the scratching of the outer layers of the skin enables the 

 pollen to come in contact with the sensitive underlying tissue 

 where it causes irritation, just as it does in nature when carried 

 by wind into contact with the delicate membranes of the nose, 

 throat and eyes. 



Particulars of the tests, which were performed at Bloemfon- 

 tein on March 9, 1921, are given in the following table: — 



