Secondhand smoke mainly contains nicotine, tar and other harmful chemicals and carcinogens, which are more harmful to children than firsthand smoke. Because children belong to the growth period, all aspects of the body are not yet developed, second-hand smoke will seriously jeopardize the health of children. Secondhand smoke affects a child’s respiratory system, inducing asthma or aggravating asthma in children. Generally speaking, children whose parents smoke are more likely to suffer from asthma than those who don’t, and it can also increase the risk of respiratory diseases in children. Studies have shown that children who have been passive smokers for a long period of time have significantly poorer mental development than children raised in non-smoke environments. Prolonged exposure to secondhand smoke can cause dizziness, memory loss, and some neurological effects in children. Secondhand smoke can cause chronic pharyngitis. Tar, nicotine, nicotine and other harmful substances in smoke can inhibit the activity of respiratory cilia, so that the purification capacity of the respiratory tract is weakened, bronchial mucosa congestion, edema, repeated infections resulting in chronic pharyngitis. Evidence suggests that exposure of children to second-hand smoke before, during and after birth can lead to leukemia, lymphoma and brain malignancies.