Let’s break it down.
What you think of as ‘sunshine’ is actually a combination of three different kinds of ultraviolet rays – UVA, UVB, and UVC. UVC rays are absorbed by the ozone layer and do not enter the atmosphere, so you don’t have to worry about them. However, both UVA and UVB do penetrate the atmosphere and play an important role in conditions that we could really do without (like premature skin aging, eye damage, cataracts, and skin cancer).
These rays damage both the outer and inner layers of the skin. UVA rays – the more abundant of the two forms – are generally less intense (but no less damaging). They penetrate deep into the dermis – the skin’s thickest layer – and lead to premature skin aging, wrinkling, and a suppressed immune system. Meanwhile, UVB rays burn the shallower layers of the skin – the epidermis – and are responsible for skin reddening, sunburn, and over time, skin cancer.