Tacrolimus includes oral and topical applications, which have different types with different side effects and cannot be generalized. Tacrolimus, the name of the western drug, belongs to the immunomodulators, which are divided into two types: oral and topical. The oral dosage form is clinically used for the prevention of graft rejection after liver or kidney transplantation, and for the treatment of graft rejection after liver or kidney transplantation that cannot be controlled by the application of other immunosuppressive drugs. The topical dosage form is used as a short-term or intermittent long-term treatment for patients with moderate to severe atopic dermatitis who are contraindicated by the use of conventional therapies due to potential hazards, or who have not responded adequately to, or are unable to tolerate, conventional therapies. 1. Oral tacrolimus: dizziness, headache, nausea, vomiting, generalized fever, etc. may occur after taking tacrolimus, and some patients may develop erythema, papules, generalized itching and fever. 2. Topical tacrolimus: the first few days after application may cause local skin irritation, redness, swelling, burning, itching, etc. A few patients may have ulceration, vesicles, exudation, etc. Therefore, it is recommended to follow the doctor’s instructions to standardize the use of medication, to avoid unauthorized use of medication, the emergence of side effects is not conducive to the recovery of the condition.