Cold medicine should not be taken together with coffee. The metabolism of caffeine will interact with the metabolism of most cold medicines produced in the body, and this effect may lead to an increase in the effects of caffeine as well as side effects, or it may lead to an increase in the effect of the drug, and likewise may lead to a decrease in the effect of the drug, either effect will have a negative impact on the treatment. It may bring the following hazards: 1. It may cause a rapid increase in blood pressure. Most cold and flu medicine will contain phenylpropanolamine, high content of caffeine products once taken at the same time with this substance, can lead to a maximum increase of three times the blood concentration, thus inducing a rapid rise in blood pressure, if the situation is serious may also be life-threatening; 2, will damage the gastric mucosa, anti-cold medicine is composed of vasoconstrictor, antipyretic and analgesic, cough expectorant, central excitatory antihistamines, etc. together, coffee Caffeine in the original will stimulate the gastric mucosa, if the combination of the two will be a great stimulation of the stomach, intensifying the adverse reactions leading to pain.