A rash from a cold is considered to be caused by a viral infection. In this case, you should first actively treat the cold and apply antiviral medication, curing the cold is the most basic way to eliminate the rash. Commonly used antiviral drugs are Banlangen granules, Oseltamivir capsules, in addition to the regular cold granules as well as cold capsules should also be taken. At the same time, we should pay attention to drink more water, eat more vegetables and try to eat less food containing high protein to prevent aggravating allergy because of protein. In addition, if the rash is more and more aggravated after taking the drugs, you should go to the hospital promptly and consult the respiratory medicine or infectious disease department.