Final answer:
Phototherapy is used to treat diseases such as multiple sclerosis, various cancers, viral infections, roundworm diseases, intestinal tapeworm infections, and Hansen's disease.
Step-by-step explanation:
The diseases that are treated by phototherapy include multiple sclerosis, various cancers (such as melanoma), and viral infections (such as Hepatitis B and C).
Phototherapy uses UV light to disrupt cell reproduction or kill bacteria. It can also trigger the production of vitamin D in the skin. For example, phototherapy is used to treat infantile jaundice by helping prevent the buildup of bilirubin in the blood.
Other diseases treated by phototherapy include roundworm diseases, intestinal tapeworm infections, and Hansen's disease.