If formalin is taken orally, the main symptoms are burning sensation in the oropharynx, esophagus and stomach, oral erosion, dysphagia, severe pain, vomiting and diarrhea, and in severe cases, gastrointestinal erosion or perforation may occur; if formalin is inhaled through the nose and mouth, the patient will experience dizziness and fatigue, and in severe cases, coma, shock, acidosis, hepatic and renal impairment, and acute renal failure; patients allergic to formalin may experience swelling of the face, and bronchial asthma, and other symptoms.