Question: You said that you have that it is possible for someone with very dark skin to get sunburn but we can't see it, how come we can't see it with the human eye?

Barbara Shih answered on 13 Mar 2015:

The sunburn response (normally seen as the skin going red) is usually characterised by an increase in the size of blood vessels (and increase in blood flow) and the recruited immune cells. This tends to happen in the dermis (lower layers of the skin). In dark skin, there is a layer of melanin at the on top of the dermis. Melanin are pigments that absorbs light, and also what makes skin look dark. The reason why you can’t see the sunburn is because it is a little bit like placing a dark colour filter on top of a red circle – the red circle is always there, but it’s harder to see with colour filter on top of it.

We can still see other sunburn responses, such as skin peeling. Some of my participants mentioned that they have been burnt (peeling) before, just couldn’t see it.