A 3mm proliferative foci on the lungs is not scary. The proliferative foci on the lungs are formed when the lung fibrous tissue repairs and wraps around the damaged area during the recovery period after the lungs are damaged, which belongs to the tissue reparative changes and is common in tuberculosis patients. A 3mm proliferative foci usually has little effect and patients may not show any clinical manifestations. Tuberculosis patients can take isoniazid, rifampicin and other anti-tuberculosis drugs under the guidance of doctors. Isoniazid is contraindicated in patients with allergies and hepatic impairment, and the adverse effects of isoniazid include peripheral neuropathy and liver injury. Rifampicin also cannot be used in patients with allergy and severe hepatic insufficiency, and it is also contraindicated in women in early pregnancy and in patients with biliary obstruction, with adverse reactions such as burning sensation in the stomach, nausea and vomiting. Patients with 3mm proliferative foci on the lungs should go to the hospital in time for observation and follow-up or treatment according to the doctor’s instructions and recommendations.