Prolonged exposure to ultraviolet light, UVA or UVB, from sunlight can lead to:
The Types of UV Rays
Sunlight contains three types of ultraviolet rays: UVA, UVB, and UVC.
SPF Protection Explained
Besides avoiding unnecessary sunlight exposure (especially from 10am to 3pm), another method to protect yourself is to use a protective sunscreen in order to minimize the penetration of the sun’s UV rays.
However, recent research shows that people who buy sunscreens are not sure exactly on the technical terms on their labels such as the SPF figures. They mistakenly believed that higher SPF ratings meant stronger UV protection, not longer protection.
SPF, an abbreviation for sun-protection factor, is a number such as 15, 30, or 50 that indicates the degree of sunburn protection provided by sunscreens. SPF is related to the total amount of sun exposure rather than simply the length of sun exposure. The amount of sun exposure depends upon a number of factors including the length of exposure, time of day, geographic location, and weather conditions. The SPF numbers make it easier for people to choose the sunscreen best suited to their complexions and conditions of exposure.
The chart below shows a chart on SPF values for various skin types depending on the amount of sunlight you are exposed to.