Usually fluoride is not recommended when you have a cold. Fluoride itself is an organic compound that is good for dental development and bone growth, but if it is consumed in excess, it can lead to fluorosis. Moreover, fluoride is a substance that should not be taken together with many cold medicines. If applied together, it will lead to secondary failure of cold medicines and some adverse reactions of fluoride, such as memory loss, dizziness, nausea, vomiting, loss of appetite, etc., will occur in the early stage. So when you have a cold, if you only have some symptoms of nasal congestion and runny nose, you can drink a lot of warm water and take certain cold medicine at this time, but you should not apply fluoride. When the cold is serious, the fluorine will be absorbed by the body, which will only stimulate the metabolic reaction and aggravate the cold, so the fluorine should not be applied when you have a cold.