What does SPF mean? All sunscreens in the UK are labelled with the letters SPF. SPF stands for sun protection factor. The SPF number is determined in lab tests by exposing skin to a light spectrum that mimics the level of UV at midday. The SPF is the level of protection that is offered against UVB (it’s the measure of time that you can stay in the sun with sunscreen on before redness occurs on the skin). So if you are a person who would start to burn after about 10 minutes in the sun without sunscreen then by applying an SPF 15 (10 minutes till burn time x 15 spf = 150) you would gain 150 minutes of UVB protection. UVA & Star System On sunscreens purchased in the UK you will find the UVA logo (“UVA” printed in a circle) accompanied by up to 5 stars.The UVA logo indicates that the UVA protection is at least a 1/3 of that of the SPF.The stars indicate the amount of UVA rays absorbed by the sunscreen in comparison to the UVB. So if you purchase a sunscreen with a low SPF, it might hav...