Onions are a commonly consumed vegetable and have many health benefits. The onions are not recommended for people who have poor gastrointestinal function, or for people who have Yin deficiency or allergies. 1. poor gastrointestinal function: onions are easy to produce gas, and too much of them can easily produce gas in the gut, leading to abdominal pain and bloating. The onion is spicy and stimulating, which can easily stimulate the gastrointestinal mucosa and cause pain in the gastrointestinal area; 2. Yin deficiency body heat: from the perspective of Chinese medicine, the onion is a hot vegetable, which can easily strengthen the dry heat in the body after consumption and produce fire. Yin deficiency body heat will aggravate the heat in the body after consumption, which may lead to sore throat, mouth ulcers, etc.; 3, allergies: allergy-prone body needs to avoid eating onions, onion juice is easy to stimulate the skin, if allergies will lead to itchy skin and accompanied by a rash; 4, eye diseases: because of the strong volatility of onion juice, when the juice touches the area around the eyes will produce serious eye discomfort symptoms. At this time not only irritate the eyes, but also may aggravate eye diseases. In addition, onion itself is spicy is not recommended to be eaten at the same time with other spicy foods to avoid doubling the stimulation of the stomach and intestines. Because onions contain oxalic acid, it is not recommended to eat them with foods that contain more calcium, such as soy products, to avoid hindering calcium absorption.