In Nakuru, a secondary city in Kenya, herbal doctors argue that African bodies are infested by ‘dirt’. Gathering at crossroads, they teach about the dangerous effects of processed foods on African bodies. During public product demonstrations, they patch together urban gossip, kemikali (chemicals in Kiswahili) and consumer goods from abroad to demonstrate their overheating effects on stomachs. In this article, I think through metabolism and digestion to demonstrate how ‘navigating’ urban toxicity in Nakuru implies a bodily praxis that hinges on debates about the porosity of the nation's borders responding to the afflictions of globalization. I show how the occult character of kemikali pivots on the collapse between insides and outsides, leading to overheating stomachs, and consequently argue that herbal interventions coating the lining of the stomach and the gut do what national borders are unable to achieve: keeping out toxic intrusions. From this point of view, herbal practices in Nakuru demonstrate agency and resistance to worlds perceived as increasingly toxic and polluted.