ABSTRACT
The immune system is essential for maintaining good health, as it destroys the majority of
cells that develop abnormal or cancerous properties in addition to infectious agents,
including viruses, bacteria, and parasites. Only tumor cells that fail to be eliminated by the
immune system develop into a clinical cancer, and even then, they are controlled by the
immune system, and sometimes even regress (1). As the skin is our external barrier, it is
exposed to environmental insults in addition to receiving direct exposure to high levels of
potentially infectious agents. It therefore needs a very effective immune system to deal
with these health hazards. Ultraviolet radiation (UVR) in sunlight is probably the most
dangerous environmental insult that the immune system of humans is exposed to. It
suppresses immunity at exposure levels that are only 0.25 to 0.5 of those required to cause
sunburn. It is therefore very important for sunscreens to provide a high level of protection
to the immune system. A key challenge is how to protect the immune system from UVR
without detracting from the beneficial effects of sunlight such as vitamin D production.
