Reiki Healing does not claim to cure illnesses but is used as a complimentary therapy with other mainstream therapies. In essence, Reiki is the art of moving energy in the body to areas where energy has failed to flow through sufficiently. Emotional issues such as stress, depression, anger and frustration can and do cause these blockages and allow illness to manifest within the body.
The process of illness and disease manifest through this process. Through our soul we can bring limitation from past lives. Through this spiritual body, limiting imprints can manifest within the mental mind as it then creates suffering through beliefs and the ego self. It can then create the emotions associated with these mental limitation which energetically effect the physical body as disease.
Reiki is a highly effective therapy because it is about eliminating the very limiting imprints from the mental, emotional and physical aspects of the self so the soul can purify itself and escape the cycles of suffering. The physical dimension essentially is a place where we can become spiritually contaminated. And the aim of living in harmony with the universe is to purify the self so one can live in peace, harmony and well being.