Radiotherapy emits high-frequency waves to a specific target (the cancer cells). The targeted cells are in turn killed. However as the waves have to pass through skin, at the point of entry, and the point of exit, skin is often affected. This is because radiotherapy targets all cells, it is not selective, so any cells, including skin cells, can be injured. Describing how radiotherapy affects the skin can be compared to the sunlight and becoming sunburnt. Depending on the different colour of skin, and the location of the skin, too much sunlight can lead to you becoming burnt. And sunburn can also vary; some people experience mild sunburn that goes away or is easily managed with creams, while some people experiencing extreme sunburn that damages the skin. People also forget that unlike the sun, radiotherapy isn’t absorbed, so as well as having an entry site, the rays also exit the body via the skin. Therefore if you are having radiotherapy to your breast, for example, you may find the skin on your shoulder and back become red and irritated if not managed.