It is generally known that it is a good idea to wear a sunscreen when outside for an extended period.
Over recent times there has been a concern that many people are vitamin d deficient due to lack of sunlight.
One approach is to wear sunscreen on the areas of your skin that have seen a lot of sun exposure over time eg the face,hands and arms and try to expose areas that are not so frequently exposed eg the trunk. This may be difficult in very cold weather.
It should be noted that one cannot burn behind glass and also the beneficial ultraviolet rays that produce vitamin d in the skin do not get through the glass.
Generally sun exposure for less than 20 minutes does not need a sun block and it also allows one to get a degree of sun exposure to produce vitamin d.
For some people these suggestions do not work very well. In this situation oral vitamin d supplements can be used.
It has been shown that a low vitamin d level can make an individual more prone to develop sun spots and perhaps some skin cancers. Thus it is well worthwhile paying attention to one’s vitamin d levels but at the same time not overdoing the sun.
It is a matter of taking a balanced approach to sunlight and protection.
Interestingly this is also the portion of sunlight that produces vitamin d in the skin.
There is also another band of ultraviolet light-ultraviolet a.This does not usually cause burning.Ultraviolet a can penetrate quite deeply in the skin and in the longer term causes skin ageing and wrinkles. It may also have a lesser role than ultraviolet b in producing skin cancer.
Sunscreens have different components that block ultraviolet a and ultraviolet b.
Sunscreens that block both are called broad spectrum .These days most sunscreens are broad spectrum.
The spf factor of a sunscreen refers to its ability to block ultraviolet b.Many sunscreens today are spf 30 to 50. A sunscreen with a spf 30 is quite adequate for individuals that have normal sun expsosure,however those who spend long periods outside a spf 50 may be more useful.
Reapplying sunscreen after a time is needed especially if one sweats or is immersed in water.Sunscreens for these situations are available that have greater water resistance –often up tp 4 hours.Reapplication is necessary after this time to maintain adequate protection.
At one stage concern was raised that sunscreens could be absorbed from the skin and cause internal toxicity.
A large number of studies have failed to find internal toxic effects from sunscreens.