Are you wondering what does SPF mean? The initials SPF stand for Sun Protection Factor. The higher the SPF number on sunscreen, the more protection you have, or the longer you can stay in the sun without burning.
You may note that any product that carries an SPF claim will have a list of "active ingredients" - those are the ingredients that give the product it's sun protection - it doesn't mean those are the only "active" ingredients - in that they don't do anything.
The SPF number tells you how long you can stay in the sun before getting burned. If you normally start to burn after 15 minutes of sun exposure, an SPF 15 product will let you stay in the sun for approximately 15 times longer (or 3 1/2 hours) without burning.
SPF sunscreen numbers indicate sunburn protection from UVB rays only. There is not a rating system for UVA.
Skin damage is caused buy both UVA and UVB exposure. Sunlight exposes you to two kinds of ultraviolet light, called UVA and UVB. Both can cause skin damage, including wrinkling and skin cancer.
Exposure to UVB rays has an immediate (within 60 seconds) and harmful effect to the skin.
You don’t feel or notice UVA exposure but it is the main cause of skin cancer and wrinkles, one of the main reasons why sunscreen is important.
To ensure protection from UVA rays your sunscreen should be labeled “Broad Spectrum” and contain at least one of these ingredients:
Avobenzone (also known as Parsol 1789 or butyl methoxydibenzoylmethane)
Helioplex (Is the Neutrogena blend of Avobenzone and Oxybenzone)
15 + 15 does not equal 30 – Layering SPF products does not increase the total number or the effectiveness.
Drs. Christiaan Janssens