HYPERSENSITIVENESS 571 



b. Conjunctival Tests. — In cases of pollen hay fever a dilute 

 solution of the pollen under suspicion is dropped into the con- 

 junctival sac. If no reaction occurs within five or ten minutes, the 

 pollen is not incriminated. When a positive reaction occurs, it ap- 

 pears as a diffuse reddening of the conjunctiva accompanied by 

 itching and a watery discharge. The intensity of the reaction can 

 be controlled by dropping into the conjunctival sac either adrenalin 

 (1:5,000) or cocaine (2 per cent). 



c. Scratch tests are performed on the back, al)domen or arms 

 of the patient. Alexander (1930) demonstrated considerable varia- 

 tion in skin reactions (intradermal) for different regions of the 

 body. The skin of the back and abdomen is apparently preferable 

 to the skin of the forearm. The technique employed by Rackemann 

 in performing scratch tests is described by him as follows : Drops 

 of slightly alkalini7.ed salt solution or Coca's extracting fluid are 

 placed at least one inch apart on the skin. Powdered allergen is 

 I'emoved from its bottle by means of a number 4 (large size) three- 

 cornered, straight surgical needle and stirred into a drop of solvent 

 after thorough mixing. The needle is used to make a short scratch, 

 about 3 mm. long, through the drop of solution. The needle is 

 then wiped thoroughly with gauze soaked in alcohol and used to 

 test another allergen in the next drop of solvent. 



d. Puncture Test. — In the puncture test the reagin extract is 

 prepared as for the scratch test. Instead of making a scratch 

 through the drop of extract, a few skin punctures are made with 

 the .sharp point of a darning needle. 



e. Intradermal Test. — The intradermal test is employed by 

 many specialists in allergy. In performing this test one must em- 

 ploy sterile, standardized allergen extracts and preferably a 

 separate, all-glass, accurately graduated tuberculin syringe for each 

 extract. Rackemann employs sterile No. 26 gauge needles and in- 

 jects not to exceed 0.02 c.c. of each allergen extract intradermally 

 as in the Mantoux test. 



f. Patch Test.— It has been found that in practically all cases 

 of contact dermatitis the exciting agent will give a pasitive skin 

 7'eaction if it is kept in contact with the skin, whereas negative re- 

 .sults are obtained (juite fre([uently when the scratch or intradermal 



