1) UVA rays cause cancer.
2) UVA rays cause premature aging of the skin including wrinkles and sagging by destroying the elastin and collagen in your skin.
3) UVB rays cause painful and serious burning of the skin.
4) A base tan does not protect your skin from UVA or UVB rays
5) Tanning in a tanning bed is as bad or worse than tanning in the sun.
Fortunately, we have these wonderful products that can prevent all of these from happening. They're called sunscreens. There are two types of sunscreen ingredients; chemical blockers and physical blockers. Now before you start raging about putting CHEMICALS on your skin, please refer to my post on why chemical free anything is a lie. Ok, so now that we have that out of the way- chemical sunscreens work by absorbing UVB and in some cases UVA rays. Physical sunscreens work by forming a physical shield that blocks both UVA and UVB rays. A good sunscreen will provide both UVA and UVB protection and it will say "Broad Spectrum" on the package. Sunscreens that claim an SPF value must be validated to perform to the stated level and are sold as a drug product. SPF (Sun Protection Factor) means that for an SPF 15 product you will be protected for 15X the amount of time you would burn in with no protection. So if you would burn in 10 minutes without sunscreen, you should reapply an SPF 15 product every 150 minutes. The problem with high SPF products is that, yes, an SPF 70 product will block the sun for 700 minutes (using our previous example) but ONLY if the product remains in a continuous film on the skin that long. Which, if you're working in the garden on a sunny day and sweating, chances are slim to none that your SPF 70 product will still be an effective coating after 11 hours in the sun. In my opinion, you're better off with an SPF 30 product applied more often.
So let's review all the different ingredients that could be in your sunscreen so you can make a wise and informed decision about which sunscreen to purchase. Some ingredients can have two names, one for when used in drug products (or products claiming SPF) and another for when they are included in the formula but no specific SPF is claimed.
UVB Blockers (also have some protection against UVA but are mainly for UVB)
1) Octinoxate (AKA Ethylhexyl Methoxycinnamate) A very common chemical blocker. A recent study concluded that octinoxate and other chemical sunscreens do not penetrate the skin in sufficient concentration to cause any significant toxicity to the underlying human keratinocytes. It does have some effect as an endocrine disrupter in rats. While I would not actively avoid this ingredient based on this, I do think there are better choices.
2) Octocylene - this is an excellent option for blocking UVB rays. A small number of people do have a sensitivity to this ingredient. If you happen to be one of those who has a reaction (contact dermatitis) when using this ingredient, avoid it. Otherwise this would be my top choice for UVB.
3) Oxybenzone (AKA Benzophenone-3) As with octinoxate, oxybenzone was studied to see if it penetrated this skin in this study. It does not. Therefore, the myth that these chemicals are causing increased cases of melanoma is false. The FDA and governing agencies in Canada and the EU have approved the use of oxybenzone as a safe and effective sunscreen ingredient. The safety of oxybenzone has also been reviewed and confirmed by the Cosmetic Ingredient Review expert panel.
4) Padimate O Some preliminary studies indicated that padimate O was a phototoxic ingredient, meaning it caused cell damage or death with UV exposure (something that would be undesirable in an ingredient designed to protect you from the sun) however, multiple in vivo studies conducted in hairless mice following topical application of padimate O have demonstrated no carcinogenic effects and that padimate O reduces the number of and delays the appearance of UV-induced skin tumors.
UVA Blockers (also block some UVB)
1) Avobenzone (AKA Butyl Methoxydibenzoylmethane) absorbs all of the wavelengths of the UVA spectrum. It also degrades significantly in light, which is one of the reasons sunscreens need to be reapplied. It can be significantly stabilized by using it in combination with octocrylene or another photostabilizer. Avobenzone can also react with minerals like iron to form colored complexes that can stain.
2) Titanium Dioxide is a physical sunscreen. Most sunscreens that use titanium dioxide use nano-sized titanium dioxide because it scatters visible light less (meaning it doesn't look white, it looks clear) but it still provides UVA protection. There has been controversy over the nano-sized titanium dioxide products because as with the chemical sunscreens people are afraid that they are being absorbed by the skin and in to the blood stream where they are wreaking all kinds of havoc. As with the chemical sunscreens however, studies have show that this is not true. Titanium Dioxide is not absorbed at any significant level by the skin. As with nearly all ingredients, some people can be allergic to titanium dioxide.
3) Zinc Oxide also a physical sunscreen. It's thick, pasty and white unless nano-sized zinc oxide particles are used. Refer to the titanium dioxide discussion above.
Now for the specific points of the "controversy":
1) The absence of UVA filters combined with a longer exposure time of the sunscreen user causes more melanoma than a non sunscreen user.
- This one is easy- use a broad spectrum sunscreen. UVA rays are mostly responsible for the DNA damage that causes skin cancer. Make sure your sunscreen protects against both UVA and UVB. Recent changes to how sunscreen products are labeled ensure that only products that protect against UVA and UVB rays are labeled "Broad Spectrum"
2) By reducing the exposure of the skin to UVB radiation, sunscreen suppresses the skin's production of the natural photoprotectant, melanin, and the lack of melanin leads to an increased risk of melanoma.
- This has been disproved multiple times. Getting a base tan (increasing the melanin in the skin) offers an increase in SPF of 4 or less. The larger issue is that any darkening of the skin indicates UV damage to the skin. So you're not helping yourself, you're hurting yourself.
3) Melanoma is caused by free radical generation by sunscreen chemicals that have penetrated into the skin.
- As I have cited in this post, multiple studies have disproved the notion that any of these chemicals are absorbed in any significant amount deep enough to cause damage to the keratinocytes.
4) Melanoma is caused by the pathogenic cytotoxicity and carcinogenicity of micronized titanium or zinc oxide nanoparticles.
- Again, as I have cited in this post, multiple studies have confirmed that nano and micro sized titanium dioxide and zinc oxide do not penetrate into the skin in any significant amount to cause any health effects.
5) Malignant melanoma has been found more frequently in sunscreen users compared to non-users in some studies. Other studies found fair skinned people used more sunscreen and had more skin cancer, but did not address cause and effect.
- This is a case of confusing correlation with causation. Several metanalyses have failed to demonstrate any causative relationship between sunscreen use and cancer rates.