What do the terms UVA, UVB and SPF mean?
Sunlight is made up of a continuous radiation spectrum that is divided into various types of radiation depending on the wavelength, e.g. into ultraviolet radiation (UV), visible light or infrared radiation (IR). UV radiation is also divided into short-wave UVB radiation and longer-wave UVA radiation.
UVB radiation only penetrates the uppermost layers of the skin, but it is very high in energy and results in skin damage in the event of overexposure. UVB rays are therefore primarily responsible for sunburn.
UVA radiation has lower energy levels than UVB radiation. However, it can penetrate deeper into the skin, damaging cells and causing tissue damage. Very high exposure to UVA radiation, however, can also lead to sunburn and an increased risk of skin cancer.
"SPF" is the abbreviation for "sun protection factor". The number specifies how much longer you can stay out in the sun until sunburn occurs after using sunscreen. The natural protection time depends on the respective skin type, any pre-tan and the intensity of the sun (UV index).