slide 2 of 12. Skin The skin is the largest organ in the human body. Its main job is to maintain the body's temperature, which means that sweat is created to cool the body, and goosebumps or raised hair occur to trap heat in the body. Along with sweat glands, the skin contains oil glands.
...However, if I am wrong about that, the answer is that acetaminophen (and its metabolites) are identifiable for up to 48 hours after you took the pill. Less if you took tiny doses, but up to standard clinical doses (<8g), it's 48ish hours.
140 mg/kg body weight, orally, once as a loading dose. Maintenance Dose: 70 mg/kg body weight, orally, 4 hours after the loading dose and every 4 hours for 17 total doses, unless repeated acetaminophen assays reveal nontoxic levels.