Five or ten days after a single injection with one gram of horse serum globulin, allergic reactions, such as edema and erythema, appeared in both ears of sensitized rabbits and continued to exist for 2 to 6 days. The frequency of occurrence of the reactions was about 60 per cent. Those reactions were also induced immediately after subcutaneous reinjection with one mg of the same antigen into the unilateral ear of rabbits which had been sensitized with a smaller amount of antigen than that which might be necessary to induce such delayed type of reactions as described above.
In sensitized rabbits which had developed allergic reactions, the level of antibody against horse serum globulin in the blood stream was proved to be higher than that in rabbits which had failed to develop allergic reactions.
These allergic reactions were prevented by subcutaneous injection with cortical steroid hormones for five or ten days after the sensitization of horse serum protein. Both glycyrrhizin and ACTH were also effective to relieve the reactions.
From these experimental results, it is suggested that the mechanism of steroid to prevent allergic reactions may not be simple. One of the factors related to this mechanism is to prevent the production of antibody, and another the anti-inflammatory effect of steroid.