Where should the Sanfu patch be applied to be most effective? Summer is the best time for people to use sunglasses. Generally speaking, sticking it on the appropriate part can have a soothing effect on the body and mind. However, many people don’t know where the Sanfu patch should be applied to be most effective. So, in this article, we will elaborate on this issue from four aspects. 1. Apply to the back and belly button. The back is a large area. Applying the Sanfu patch can have a good antipyretic and detoxifying effect. When attached to the navel area, it can stimulate the meridians and circulate Qi.