You should not eat onions when you have a cough with a cold. Onions are a relatively pungent and stimulating vegetable. When an onion is cut, the tissue cells of the onion itself are destroyed, releasing a substance called alliinase. This substance then produces a special odor that stimulates the human respiratory tract, causing a more pronounced congestion and edema of the airway mucosa, and even causing an exuberant secretion of airway glands, so that not only does it not relieve the symptoms of cold and cough, but also aggravates the damage. So when you have a cold and cough, it is not recommended to eat onions, you should eat some light and easily digestible and absorbable vegetables, such as cabbage, white radish, purple kale, yellow cauliflower, etc.