No.

Sunscreen protects the skin from harmful ultra-violet (UV) radiation, type A and B. Inorganic sunscreen components like zinc reflect and scatter UV rays. Organic components, like oxybenzone, absorb the rays and turn them into heat. UV-A comes straight in through the atmosphere; UV-B is partly blocked by a good ozone layer.

Carbon dioxide does not stop much radiation from the sun. What it does do is absorb infrared radiation that rises from the warmed surface of the earth. Carbon dioxide keeps the earth warm (and is causing global warming).

If anything, the ozone layer acts like a sun screen!

Even though more people use sunscreen than ever before, the incidence of skin cancer in the United States and other countries continues to rise. How is that possible? Some scientists have a theory, and it has to do with your sunscreen. The FDA isn't regulating the industry, so there's no one to confirm the dramatic surge in exaggerated SPF claims above 50.

In a recently released report questioning the effectiveness and safety of top-selling sunscreens, the Environmental Working Group (EWG) claims that many contain potentially hazardous ingredients. In fact, they evaluated 1500 sunscreens and found only 8% to be acceptable. That's right - 8%. And a lot of those that made their "Hall of Shame" were products designed to protect the littlest consumers. In fact, five of the eight worst offenders were baby products.

One of the most common sunscreen ingredients is vitamin A, which accelerates development of skin tumors and lesions. About 60% of sunscreens contain the chemical ingredient oxybenzone, which the EWG considers unsafe because of concerns that it can penetrate the skin and disrupt hormone balance. There are several other potentially harmful chemicals found in sunscreens that are reported to increase the likelihood of skin cancers. There are no fewer than four known carcinogens found in popular sunscreen products. And what's really scary? A number of studies report higher, not lower, incidence of the deadliest form of skin cancer, malignant melanoma, among frequent sunscreen users.

So what do you do?

Ignore any claim that the manufacturer makes. Assume it's an embellishment. Instead, turn straight to the ingredient list and look for: zinc oxide, titanium dioxide, Mexoryl or avobenzone. Buying products with those ingredients offers some assurance that you'll get at least some protection from UVA rays

You may feel comforted by seeing the logo for the The Skin Cancer Foundation (SCF) on your bottle of sunscreen. Don't be. They lend its logo to hundreds of sun protection products. To get approved, all you have to do is prove your products has an SPF of 15 and don't forget to stroke a check for $10 grand to join the Foundation's "Corporate Council."

There are other things you can do to stay safe during the summer months. For example, you can stay out of the sun when it is the most intense, often from 10:00 a.m. and 2:00 p.m., but this is dependent on where in the world you live. Remember our bodies need Vitamin D, but if you're going to be outside for a long time, use shade, hats, and clothing to protect yourself.

You need to look for the cause of the discoloration under your eyes, for it is merely a symptom which will reappear in another way if you conceal or ignore it. The main problem is something that we all know about: lack of sleep. It is the primary cause for dark discoloration under the eyes. Some people require more sleep than others, and that is also affected by diet. See what works best for you, and don't compromise your sleep.

Following that, stress will wear a person down and place enough stress on the immune system that the body begins to exhibit symptoms such as this. It can be seen alongside the inability to think clearly, and even palpitations. If you are in a job that is too much for you, it is time to look in another direction. If you love it anyway, look online for some resources about meditation. Try yoga if that works for you. Each person is different, and you should harness that.

Get some sunlight. Sunlight, or Vitamin D, is not the killer that the establishment would have you believe. It is not out to get you, but that does not mean that you need to lay out in it all day long in 100 degree heat, either. Too much can be more dangerous than too little. When you go out in the sun, do not wear sunscreen. Sunscreen contains titanium dioxide, zinc oxide and oxybenzone which are all known to be incredibly damaging to the body. Be proud of your body, and believe in it. Get outside for at least 30 minutes each day before 12 or after 3.

Lastly, a huge factor can be troublesome allergies. Allergies are very common in the United States, and they are best treated with a good diet accompanied with an intake of some all-natural plain yogurt. Yogurt will help to restore the natural rythm in your intestinal tract. Allergies are usually only present alongside an overgrowth of candida, which is a type of yeast that lives in the intestines. It is fueled by sugar-based products, refined (white) carbohydrates, and various food additives. Additonally, if allergies are the problem, then using high quality anti-allergen air filters would be prudent.

Some people do not have the problems outlined above. These are other common problems which can cause shadows under the eyes:

- Dehydration. Drink when you are thirsty, and do not put it off; especially when you are out in the sun.

- Rubbing the eyes, in some people who are more sensitive. Stop rubbing, and the problem will go away if this is the cause.

The main factor is to find out the reason for it and possibly the best way is to first of all balance your health and diet as well as your sleep. Try first of all to have a diet with plenty of vegetables and fruit, drink plenty of water, spend at least 20 minutes each day outdoors, when you are indoor try to get as much natural sunlight as possible instead of artificial lights, sleep at least 8 hours a day and no more than 9 hours a day, try to have a 10 or 20 minutes nap in the middle of the day (never longer than 30 minutes), exercise regularly never arriving to exhaustion and always allow a period of 24 hours recovery with no exercising after each exercise session, reduce animal products and have plants home to oxygenate the environment.

After 6 weeks you will notice a better health and improved energy. You may also notice less darkening under the eyes. If the darkening is still there, go to a doctor and ask for a full test in hormones including adrenals (cortisol).

In the meaning time, use nutritive creams for the eyes and avoid any cream with retinol-A or indicated for peeling. A trick for makeup is to use a soft orange tone (can be from a base or lipstick) under the make up base or powder, the orange color neutralizes the blue of the darkened area.

We don't know because there aren't enough good clinical trials published looking at this. But I wound't stop using sunscreen. Bear with me for a bit and I'll try explain a few thing.

There are many things that cause cancer in this world, and there are many different "pathways" that can lead to cancer, producing many different types of cancer. At a basic level, cancer (also called neoplasia) is produced by acquired mutations in the DNA of cells that give it growth, proliferation and survival advantages. There are a number of check-points and control mechanisms in your body to prevent this happening and keep growth under control. However, with repeated exposure to cancer causing substances over time, mutations in the DNA can accumulate, knocking out these natural regulators, eventually leading to cancer as the cells proliferate, invade tissues and expand uncontrolled by the body.

Sunlight has two components of relevance here: UV-A and UV-B light. UV-B is responsible for what we know as sun-burn, the reddening, blistering and eventual peeling of the skin. UV-A is a weaker sun-burn inducing agent, but is able to penetrate further into the skin than UV-B.

UV-A and UV-B are believed to contribute to cancer in two slightly different ways. UV-B is thought to act as a cancer "initiator" by damaging cellular DNA to induce mutations.

UV-A is thought to act as a "promoter" by generating reactive oxygen species in the tissue, which damage cells and affecting their signalling pathways. So the link between the sun and cancer could be the additive effects of UV-A and UV-B, where one bad bout of sun burn is enough to initiate pre-cancerous changes in the cells (UV-B), and subsequent repeated exposure to the sun then promotes these changes (UV-A), enabling the mutations to become established and selected for in the cell populations.

There are a lot of publications on the affects of UV-A and UV-B on cell function, and its possible link to cancer. Sunscreens that offer protection agains UV-A and UV-B are effective in preventing sunburn - many people would have experienced this after being out in the sun long enough with out sun screen. But the question is, does sun screen prevent skin cancer?

My belief is that the sun is a much more powerful initiator and promoter of cancer than the products found in (good) sunscreens, in the amounts that they are present, and there is a greater risk of developing skin cancer from prolonged sun exposure (that would cause burn) without sunscreen, than with sunscreen. I haven't looked into all the ingredients contained in most good sunscreens, or the evidence of their prolonged use on humans or animal models, maybe someone else will be able to chip in here, but when looking at the evidence (such as aluminium oxide causing cancer), keep in mind that these agents will often be looked at in isolation, in an amount that far exceeds the amount humans are exposed to, administered in a different way to that of normal use, and used (at best) on an animal model that may not translate its findings to humans. The best clinical evidence comes from well designed human studies. These are few and far between (understandably due to ethical limitations).

I believe sunscreens are relatively safe (provided you buy from trusted and reputable brands). But if you want to do some of your own research, I've provided a couple as a starting point. The best sources of information are the relevant peer reviewed, transparent science journals that have declared any conflict of interest.

Sunlight, vitamin D and skin cancer

Advances in Experimental Medicine and Biology, 2008, Volume 624, 104-116, DOI: 10.1007/978-0-387-77574-6_9

Current sunscreen controversies: a critical review. Mark E. Burnett, Steven Q. Wang. Photodermatology, Photoimmunology & Photomedicine. Volume 27, Issue 2, pages 58-67, April 2011

Are sunscreens safe?

Zoe Diana Draelos MD. Journal of Cosmetic Dermatology
Volume 9, Issue 1, pages 1-2,March 2010