Formaldehyde poisoning generally does not cause fever unless the symptoms are particularly severe, such as pneumonia, or a combination of other conditions. Formaldehyde irritation reaction manifestations are generally transient, with symptoms of eye as well as upper respiratory tract irritation, such as eye stinging, tearing, sore throat, chest tightness, and coughing. In mild cases of formaldehyde poisoning, there are general symptoms such as blurred vision, dizziness, headache, and weakness. Moderate poisoning appears as persistent cough, hoarseness, chest pain, difficulty in breathing, and dotted shadows can be seen on chest X-ray. Severe poisoning will show edema of the larynx and even trigger asphyxia, pulmonary edema, coma and shock, usually combined with pneumonia, or more serious systemic secondary infection, which may cause fever.