Oxypathy is an obscure historical term for a supposed disorder in which the body fails to expel “unoxidisable acids,” which then accumulate and damage tissues. It belongs to the early twentieth-century literature of autointoxication theories, which blamed vague systemic complaints on retained metabolic wastes and justified purging, fasting, and colonic irrigation regimens. Modern biochemistry recognises no such entity: the body oxidises or excretes metabolic acids through well-characterised pathways in the liver, kidneys, and lungs, and genuine acidosis, as in diabetic ketoacidosis or kidney failure, is a medical emergency with clear diagnostic criteria. Oxypathy survives only as a dictionary curiosity and a reminder that plausible-sounding biochemical language can dress up unfounded theories, a pattern that recurs in modern detox marketing.