In TCM, the occurrence of medication allergy is not completely related to therapeutic dose, but also related to cross sensitivity and multiple sensitivity. Drug rash belongs to the category of "Drug Poison" in Chinese medicine. It is mostly related to constitutional intolerance and occurs when drug poison enters the Ying-Nutrient System and Xue-Blood System, attacks the muscle and skin, and transmits into the meridians and Zang-fu organs. Yin can be damaged by heat toxin in long duration. If the spleenfails to perform its transportation, the internal excessive dampness will fight against the drug poison to cause accumulation of heat toxin with dampness in the muscle and skin.

According to the theory of traditional Chinese medicine, there are some patterns of syndrome that lead to Drug Rash.
1. Syndrome of Heat-Toxin Invading Ying-Nutrient System
2. Syndrome of Mixture of Heat-Toxin and Dampness
3. Syndrome of Yin Impairment by Heat Toxin