There's a difference between UVA and UVB
The sun doesn't just emit one kind of kind of radiation. The sun emits ultraviolet radiation in the form of UVA and UVB. UVB are the burning rays that damage the superficial layers of the skin causing sunburn. They also play a key role in the development of skin cancer.
UVA rays penetrate your skin much deeper, causing skin ageing and DNA damage, which leads to skin cancer. In the past, UVA was considered less harmful than UVB (which causes direct DNA damage), but today UVA is known to contribute to skin cancer via indirect DNA damage. Several studies suggest that the absence of UVA filters may be the cause of the higher incidence of melanoma found in sunscreen users compared to non-users.
So you need a 'broad spectrum' sunscreen
SPF is a measure of how well a sunscreen will protect skin from those UVB rays.
SPF gives no indication of the level of all-important UVA protection. For that you need to look at the UVA star system, which should be on the back of your bottle. These stars (ranging from 0-5) will tell you the percentage of UVA radiation absorbed by your sunscreen. SPF30 sunscreen with UVA rating of 4-5 stars is considered a good standard of sun protection.
A higher factor doesn't always mean higher protection
Sunscreens with really high SPFs, such as SPF 75 or SPF 100, do not offer significantly greater protection than SPF 30 and mislead people into thinking they have more protection than they actually do. In fact, SPF30 blocks 97% of UVB rays and SPF50 blocks 98%.
Fake tan and SPF don't mix
If you've ever been tempted by those miraculous-sounding products that claim to fake tan while they protect, listen up. Abi Cleeve, managing director of suncare brand Ultrasun explains, "The primary ingredient in self tanning products is a chemical called Dihydroxyacetone (DHA). DHA works by creating a chemical reaction on your skin."
Spray sunscreens aren't always so hot
With most of our childhood beach memories involving being plastered in gloopy white cream, spray sunscreens sound amazing. However, aerosol sunscreens contain a lot of alcohol, which, breaks down photostability and dries out your skin just when you need hydration most. Avoiding it altogether in sunscreen is almost impossible. Just stear clear of products that feature alcohol among the first few ingredients in the formula and check the label when it comes to aerosols, gels and anything that claims to be 'cooling'.
Yes, you can find a sunscreen that doesn't give you spots
Dermatologist Stephanie Williams feels your pain when it comes to SPF-induced breakouts. "It's not really the UV filter itself that causes spots, it’s more how the cream is formulated around the filter. Avoid creams that have a greasy texture and don't sink into your skin after a couple of minutes. A good starting point is any sunscreen that states 'oil free' on the bottle.