Clothes can offer good protection to your skin from the sun, by way of UV Sun Protection clothing, however it is important to know that some clothes are better than others. There are many factors that affect the level of sun protection provided by a fabric. These include:
Weave - tighter weave or knit improves the rating
Fibre - polyester is often better than cotton
Colour - darker colours are generally better
Stretch - more stretch lowers the rating
Moisture - many fabrics have lower ratings when wet
Condition - worn and faded garments may have reduced ratings
Finishing - some fabrics are treated with UV absorbing chemicals
Clothing is rated on the basis of its Ultraviolet Protection Factor (UPF) which indicates how effectively fabrics protect your skin from ultraviolet (UV) rays. The higher the UPF number, the greater degree of UV protection a garment offers. A fabric with a rating of 50 will allow only 1/50th of the sun's UV rays to pass through.
This means the fabric will reduce your skin's UV radiation exposure significantly, because only 2 percent of the UV rays will get through. This is in contrast to the Sun Protection Factor (SPF) which is the rating system used for sunscreens. SPF measures the amount of time it takes for sun-exposed skin to redden, whereas UPF measures the amount of UV radiation that penetrates a fabric and reaches the skin.
In reality, sun protective clothing should always take priority over protection with sunscreens. Mainly because we usually do not apply enough sunscreen, we fail to reapply it, or it washes off.
Be smart in the sun.