Cupping is an age-old technique used in traditional Chinese medicine to stimulate acupuncture points, to promote blood flow and clear stagnant qi. Cupping is often practised alongside acupuncture but can also be used as a treatment in its own right. Cups are rounded and can be made of glass or plastic. In cupping, the practitioner creates a vacuum inside the cup and places it onto the skin where treatment is needed. The cup is left in place for anything up to 20 minutes. Often several cups are used in one treatment. Sometimes a technique known as 'sliding cups' is used. A thin layer of massage oil is spread over the skin, the cups are then placed onto the body in the usual way and slid along the muscles being treated. This sliding method helps the blood and 'qi' to flow more easily in areas of stagnation. Cupping is not painful, however, it can leave reddish patches on the skin, like circular bruises. Although these marks resemble bruises, the muscles have not been traumatised in any way. The redness on the skin indicates that there has been movement in the circulation of blood under and around the cups. Not all cupping will result in redness as this depends on the complaint being treated.