The reason why Siwu decoction tastes a little numb may be that it has added ephedra ingredients. Ephedra is a kind of Chinese herbal medicine with strong taste and numbness. Its function is to enhance the efficacy and relieve the medicinal properties, and it also has a certain health care function. When cooking Siwu decoction, adding a proper amount of ephedra will make the soup taste unique, but it may also lead to some numbness in the taste.
The pharmaceutical ingredients in Siwu decoction may also cause allergic reactions, leading to numbness in the mouth. Everyone's physique is different, and their reaction to drugs will be different.