Typical urticarial skin reactions exactly resembling in character and time sequence those described in man by Lewis and Grant were produced in guinea pigs by light skin puncture through a drop of 1:100 histamine solution.
The vascular changes preceding and accompanying the urticarial reaction could be accurately observed by looking through the ear of the guinea pig while the reaction was in progress.
“Immediate” anaphylactic skin reactions to antigenic horse serum were produced in sensitized guinea pigs by light skin puncture through a drop of undiluted horse serum. These reactions were typically urticarial resembling the histamine wheals in character but having a more gradual and chronic sequence of development.
No general anaphylactic reactions of any kind accompanied any of the skin reactions.
The anaphylactic sensitivity of all the test animals was checked at the end of the experiment by intracardiac injection of 2 cc. of normal horse serum. There appeared to be a fairly definite relation between the presence of general anaphylactic sensitivity and the production or non-production of the typical anaphylactic skin reaction. There was no relation between general anaphylactic sensitivity and the degree of production of the histamine skin reaction.