In the cupping glass, which is placed on certain areas of the body surface, a negative pressure/suction is created. Through the vacuum, the skin and the underlying structures are adducted. This leads to the extension/elongation of connective tissue and cells, stimulation of the nerve endings and the local blood circulation and lymphatic flow. This helps to relax strained muscles.
Similarly to the also mentioned ear and scalp acupuncture, organs can be influenced with this technique (reflexology).
Cupping has also a pain relieving effect (in the sense of counter- irritation) and boosts the immune system. It may be applied with diseases of the musculoskeletal system, neuralgia (nerve pain) , paraesthesia (sensory disturbance), colds and diseases of internal organs (e.g. asthma , constipation).
The above described cupping method is called dry cupping. There are some further cupping techniques such as cupping massage, where the cupping glass is pulled over a previously oiled skin region, which has a very soothing effect on body and soul.