HIV and MS; Black skin and cancer; Iron overload; Losing your sense of smell

Dr Mark Porter finds out about the latest research investigating why people with HIV very rarely get multiple sclerosis. What does it mean for the cause of MS and possible future treatments? Also in the programme how much is black skin at reduced risk of skin cancer from exposure to the sun? Why iron overload can often go undiagnosed and the training for the nose that can help recover a lost sense of smell.