* At the first visit the following information will be collected about the participant: original diagnosis, the date and type of transplant, transplant conditioning regimen, cGVHD prophylaxis regimen, the time when oral cGVHD was first noticed, specific treatments for oral cGVHD, and any current medications.
* At each visit, and before the participant begins phototherapy treatment, they will answer a series of questions asking about how their mouth feels and what they are able to eat. A clinical examination of the mouth will be performed and recorded and photographs will be taken of the inside of the mouth.
* Participants will then receive phototherapy treatment. This will take approximately three minutes and will involve opening the mouth and closing the eyes. Following phototherapy, the participant will be asked several questions on how they tolerated the treatment. Phototherapy treatments will be done two or three times per week for a total of 24 treatments. After each treatment, if the participant has not experienced any discomfort, the phototherapy dose will be increased following a specific protocol.
* After 24 treatments the participant will have the option to continue phototherapy treatments.
