The slow reacting substance of anaphylaxis comprises the cysteinyl leukotrienes.

The investigations encompassed not only histamine, but also lysocithin (now lysolethicin) and identified a new agent, the slow reacting substance of anaphylaxis (SRS-A), plus a related SRS that was released in response to direct tissue insult.

A finding of lasting pharmacological interest from these studies was the identification and partial isolation of the slow-reacting substance of anaphylaxis.

The cysteinyl leukotrienes make up the slow-reacting substance of anaphylaxis (SRS-A).

The Slow-reacting substance of anaphylaxis or SRS-A is a mixture of the leukotrienes LTC4, LTD4 and LTE4.