The most frequent adverse reactions of ERSA, also called Gefitinib tablets, are that it causes diarrhea, rash, acne, dry skin and itching, with an incidence of more than 20%. They usually occur within the first month after taking the drug and are usually reversible as follows: 1. There is a risk of nausea, vomiting, and stomatitis, mostly mild. 2. There is a risk of dry mouth and elevated liver transaminases, mainly mild to moderate. 3. There is a risk of abnormal nails, hair loss, and allergic reactions such as angioedema and urticaria. 4. There is a risk of anorexia, weakness, and fever. 5. Conjunctivitis, blepharitis and dry eyes, as well as bleeding, such as rhinorrhea and hematuria, may occur. 6. Interstitial lung disease may occur, often serious, and fatal cases have been reported. 7. Elevated blood creatinine index, proteinuria, cystitis, etc. may occur without symptoms. It is necessary to pay attention to the observation during the medication and consult the doctor promptly if there is any abnormal performance.