Excessive formaldehyde may cause nosebleeds. Formaldehyde can directly stimulate the nasal mucosa induced nosebleeds, if prolonged exposure may also cause hematopoietic disorders, indirectly lead to nosebleeds. 1. Direct stimulation of nasal mucosa induced nosebleed: formaldehyde is a kind of toxic gas with strong irritation, long-term exposure to formaldehyde will make the capillary wall of the muscle fibers become brittle, the nasal mucosa is stimulated to produce acute inflammatory reaction, mucosal edema, and the nasal cavity is rich in capillaries, the nasal mucosa is relatively thin, it is easy to rupture bleeding. 2. Induce hematopoietic system diseases: long-term, serious formaldehyde exposure may damage the human hematopoietic system, induced by the corresponding diseases, so that platelet content is reduced, coagulation dysfunction, repeated nosebleeds. Formaldehyde is extremely harmful to human body, and has damaging effects on many body systems. Daily life should try to avoid contact with it, if the exposure to formaldehyde after the emergence of uncomfortable situation should be dealt with in a timely manner to the hospital.