Applying a medical conception of toxicity to speech practices, this paper calls for an epidemiology of discursive toxicity. Toxicity highlights the mechanisms by which speech acts and discursive practices can inflict harm, making sense of claims about harms arising from speech devoid of slurs, epithets, or a narrower class I call 'deeply derogatory terms.' Further, it highlights the role of uptake and susceptibility, and so suggests a framework for thinking about damage variation. Toxic effects vary depending on one's epistemic position, access, and authority. An inferentialist account of discursive practice plus a dynamic view of the power of language games offers tools to analyze the toxic power of speech acts. A simple account of language games helps track changes in our dis-cursive practices. Identifying patterns contributes to an epidemiology of toxic speech, which might include tracking increasing use of derogatory terms, us/them dichotomization, terms of isolation, new essentialisms, and more. Using this framework, I analyze some examples of speech already said to be toxic, working with a rough concept of toxicity as poison. Finally, exploring discursive toxicity pushes us to find ways that certain discursive practices might "inoculate" one to absorbing toxic messages, or less metaphorically, block one's capacity to make toxic inferences, take deontic stances that foster toxicity, etc.