Carbon monoxide poisoning tends to produce nonspecific, flu‑like symptoms from the brain and body not getting enough oxygen. The most typical early signs reflect this brain hypoxia: headache and dizziness, often accompanied by nausea and a feeling of weakness. This combination—headache, dizziness, nausea, and weakness—best captures how people usually feel with initial exposure, making it the best choice. Cyanosis, or a blue discoloration, isn’t a reliable early indicator, and loss of consciousness happens only in more severe cases after prolonged exposure. The set of symptoms you’d expect with an infection, like cough, fever, and rash, points away from CO poisoning and toward other illnesses. If CO exposure is suspected, move to fresh air and seek medical help promptly.