A four-year-old child may get sick twice a day for three days considering that it is related to environmental factors, weaker immunity and organic diseases. 1. Environmental factors: indoor living environment is not well ventilated, or densely populated places where there are cross-infections with each other, which may lead to four-year-old children get sick twice a day. 2. Weak immune function: As the immune function of four-year-old children has not completed development and maturity, the number and activity of immunoglobulin, complement, lysosomes and so on are more different from that of adults, and the immune system is weaker, which may lead to four-year-old children getting sick twice a day. 3. Organic diseases: including immunodeficiency diseases, congenital developmental abnormalities, infectious diseases such as pyothorax, sepsis, perianal abscesses, urinary tract infections, etc., may lead to four-year-old children two days sick. There may be other reasons for a four-year-old child to be sick twice a day, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment.