Common adverse reactions to Cycloserine can include allergic reactions, neurotoxic reactions, and cardiovascular reactions. Cycloserine belongs to the second-line anti-tuberculosis drugs, mostly used for the treatment of infections with drug-resistant Mycobacterium tuberculosis. 1. Allergic reaction: after patients take the drug, redness, swelling and rash may appear on the surface of the skin, accompanied by itching. Respiratory tract may be caused by laryngeal edema causing tightness of the throat, difficulty in breathing, swallowing and vocalization, accompanied by wheezing, abnormal hoarseness and other symptoms. 2. Neurotoxic reaction: Because of the strong neurotoxicity of this drug, it may cause dizziness, headache, speech disorders, tremor, convulsions and other symptoms in some patients, accompanied by confusion, memory loss, disorientation, personality changes, triggering irritability, epilepsy, sensory abnormalities, hyperreflexia, or coma and other symptoms. 3. Cardiovascular reactions: mainly caused by neurotoxic reactions, can be seen in sudden congestive heart failure, shortness of breath, fever, nausea, vomiting and so on. This drug is recommended to be used under the guidance of a doctor, not blindly self-medication to avoid adverse effects.