Selenium is an important trace element in the human body, selenium supplementation also has certain side effects: first of all, selenium supplementation can improve the body’s immunity, if a large amount of selenium supplementation will cause the phenomenon of hair loss, but also cause nausea, dizziness symptoms. Secondly, if a large amount of selenium is easy to trigger the symptoms of selenium poisoning leading to the human body depot, taking too much will cause the appearance of inflammation, some patients with selenium supplementation, the use of too much dose at once will lead to easy sleepiness, tiredness or headache symptoms, serious damage to the plant nerves, selenium supplementation needs to be gradually increased. If the people with bad liver take a lot of selenium supplementation, leading to the appearance of kidney disease, there are many adverse reactions to selenium supplementation, people who need selenium supplementation must be alert.