Abstract: Recently, antimicrobial secretions acting in the environment of an organism have been described as external immune defence. Here, I review evidence that antimicrobial secretions from two exocrine glands of ants, the venom gland and the metapleural glands, indeed function as external immune defence in order to increase the livelihood and hygiene within the colony. I will argue that the evolution of external immune defence has likely been favoured in social insects due to their lifestyle, i.e., due to their often long-lived and large societies, with permanent nests and the potential storage of food. Although external immune defence is widely documented for social insects, we still lack a better understanding of how external immune defence integrates into other parasite defence traits of social insects and general host physiology. Therefore, I will point to potential limitations and shortcomings of our current knowledge on external immune defence in insect societies and highlight potential new avenues for future research.