Reflexology is based on the premise that there are areas on the feet, called Reflex Zones. Massaging a certain reflex zone on the foot will send a message, through the nerves, to the brain or spinal cord, which in turn sends a message, or "reflex", to the corresponding organ or gland. This message encourages the organ or gland to relax and release tension, leading to increased blood and lymph circulation, increased nerve conduction, better cellular function and elimination of cellular waste products. It can lead to reduced swelling, especially in the feet. It also results in a soothed nervous system and helps the body to heal itself. Case studies have shown that reflexology can be an effective complementary therapy for many conditions, including asthma, hypertension, headaches, digestive problems, gout, and nervous system disorders, to name a few.