Hydroxyurea, a commonly used oral chemotherapeutic drug, is often applied in the treatment of various types of myeloproliferative disorders, such as chronic granulocytic leukemia, essential thrombocythemia, and true erythrocytosis. Meanwhile, for acute leukemia patients, if the white blood cell count is seriously over the standard, hydroxyurea can also be applied to reduce the white blood cell treatment. However, long-term use of hydroxyurea tablets can cause significant side effects. The first side effect is hematological toxicity, after taking hydroxyurea, it can cause a reduction in the number of blood cells, and the degree of reduction is closely related to the dose of hydroxyurea, if it is severely reduced, the patient may suffer from infections, bleeding and other obvious side effects. The second side effect is that some patients who take hydroxyurea for a long period of time may also develop symptoms such as mouth ulcers and tongue inflammation, as well as hyperpigmentation of the nail beds, which are very common side effects.