Clothes can provide UV coverage. Usually, lighter colours and lightweight fabrics give little protection and a T-shirt is considered to be moderately protective. Specially designed sun-protective garments offer an alternative form of UV filtration and their level of effectiveness is rated according to the UPF (Ultraviolet Protection Factor) system that measures both UVA and UVB coverage. Factors that determine the UPF rating include the fabrics weave, colour, weight, stretch and wetness retention. During the manufacturing process, fabrics are also treated with UV absorbers to enhance their sun-protective effect. Darker coloured fabrics tend to provide greater protection than lighter colours. If you are interested, look for a garment with an UPF of at least 15. Make sure to still apply sunscreen to areas of exposed skin 15 to 30 minutes prior to going outdoors.