John R. Tkach, M.D.
300 North Willson, Suite 203B
Bozeman, MT 59715
(406) 587-5442

Sunscreens: Protecting Your Skin from the Sun

Patient Information Sheet

Repeated sunburns and excessive sun exposure damage the skin causing three problems:

  1. Sunburn
  2. Chromosomal damage leading to skin cancer
  3. Aging, wrinkles, fragile skin, and easy bruising

The single most important thing you can do to protect yourself from these problems is to use a sunscreen. The cause of these problems is excessive ultraviolet light exposure.

Ultraviolet light is invisible and has no feeling of heat. When you are getting UV exposure, you don't know it. The damage is insidious (hidden). You just do not know that you are getting damage unless there is sunburn.

While you cannot see UV light, bees can see it. They polarize light with the lenses of their compound eye and use that for directions to navigate from hive to flowers and back. If the bees are out, the UV light is there.

UV light has no feel to it. When you are in the sun and feel hot, that is infrared heat, which generally does not damage skin. You can be outside on a cold or cloudy day and get sun damage.

UV light is not blocked by clouds or swimming underwater. Many people get sunburns on cloudy days.

In addition to the sun coming from above, you are getting reflected light hitting the ground and bouncing up from below. Snow and sand reflect it 100% giving you a double dose of UV. Water reflects it 75%. Grass reflects it 45%. Skiing, visiting the beach, and fishing are likely to cause sun damage. Even cutting the grass can be a problem. Wear a hat, but also use sunscreen.

How to Protect Your Skin from the Sun

What does all this mean? Must you become a hermit and stay indoors? Not at all. It is okay to be in the sun if you use sunscreen and protective clothing. We chose to live in Montana to enjoy the outdoors.

Ultraviolet light from the sun is most intense when the sun is high in the sun. The danger times are about 10 AM to 2 PM on standard time and 11 AM to 3 PM on daylight savings time. If you are trying to tan, go out early in the morning or late in the day.

There are two kinds of Ultraviolet light, UVA and UVB. UV B is blocked by window glass and the glass in you car windshield and windows. That is, you are protected with the windows up. UVA passes through window glass. So, having the windows up does not protect you.

Some eyeglasses and sunglasses protect you and some do not. Check the label. I have seen 4 or 5 people who got hidden melanoma of the retina. Those melanomas were found by their ophthalmologists on routine exams. There was nothing wrong with their vision. You can have melanoma in your eye and not know it.

UVB is the main portion of UV light. It is absorbed by the thin upper layer of skin cells, the epidermis. The damage occurs there in the basal cell layer where the epidermis grows from. This damage accumulates over many sun exposures or even just one bad sunburn. Eventually, that sun damage initiates skin cancer in the epidermis.

The more sinister UV is UVA. It passes through glass and the epidermis and penetrates down to the level of the hair roots. It can initiate cancer deep in the skin in the hidden lower wall of the hair follicle. It penetrates so deeply you do not know it is initiating cancer there until the cancer is advanced.

UVA damages the collagen and elastin fibers in the dermis, the layer just under the epidermis. That's what causes wrinkles and aging of the skin. This is the UV used by sun tanning parlors. The American Academy of Dermatology and the Skin Cancer Foundation are very strongly opposed to sun tanning parlors.

I have seen some ladies who used sunscreen faithfully, and after 7 years, the fibroblasts repaired their damaged collagen causing them to look much younger. Really, 20 years younger.

Whether basal cell cancer, squamous cell cancer, melanoma, or other skin cancers, it is this damage from sun that initiates skin cancer in this progression:

Initiation (UV damage) -> Conversion to cancer -> Promotion (local growth) -> Spread (Invasion and metastases)

Cancer does not occur overnight. The time from a sunburn to the conversion to cancer can be 5, 10, 20, 40, 60 years, a long time. This means you should see a doctor at least once a year and check your ownself monthly at home. Now you know why I am so obsessive compulsive about checking you over head to toe and using a microscope head to waist.

Dr. Tkach's Theory of Treating Cancer: Contained within each cancer cell is the mechanism for its own self destruction (apoptosis).


Using sunscreens is the single most effective thing you can do to prevent skin cancer. Keep in mind 1 million Americans get skin cancer a year. Yes, it could happen to you. Summer 2009, four medical doctors came to see me with melanoma. No one is safe from cancer.

At the end, I listed the variety of ingredients used in sunscreen. Doctors are not supposed to recommend specific brands. So, I won't. However, if you want to know what I use after 36 years of searching for a good sunscreen, I use Neutrogena Ultra-Sheer Dry Touch SPF 100. I put it on as a routine in the morning after shaving and brushing my teeth. Some people have trouble with organic chemical sunscreens. Look for titanium dioxide and/or zinc oxide. It looks white, but it works. Another nice sunscreen is Presun 45 Gel. It is sold under the counter at Walmart. Just ask the pharmacist.

People with lupus erythematosus and drug-caused photosensitivity should use a high number SPF that blocks against UVA and UVB. I think everyone should.

Correcting Myths about Sunscreens

Myth 1. I should get a suntan at a sun-tanning parlor before vacation. Wrong, here's why. The darkest suntan is an SPF of 4. I want you to use SPF 100. A suntan cannot do that.

I used to work the E.R. at Queens Hospital in Honolulu and at Kaiser Permanente Hospital on the beach at Waikiki. I have seen terrible sunburns. We are talking prednisone, morphine, I.V. fluids, and hospitalization. If you have that happen to you, your vacation is over. It will not get better in two days. It will take at least 1-2 weeks for you to recover. You just blew $5,000. Everyday of your vacation put on sunscreen first thing in the morning. That way, however the day unfolds, you are ready. Enjoy your vacation.

Myth 2. Don't use sunscreens because they cause cancer. I did extensive literature searches, talked to the head of the sunscreen division of the FDA, and to many authorities. This is absolutely untrue. It appears to be a vicious lie spread on the Internet.

Myth 3. Anything above SPF 15 is a waste and dry skin creams with SPF 15 are good enough. I used to believe this. More recent evidence is that the higher the SPF, the better. A dry skin lotion with SPF 15 or 30 is helpful, but SPF 100 is better.

Myth 4. Sunscreen blocks UV light so much that you do not make enough Vitamin D. This may not be a myth. This may be true. I have changed my stand on this. I take 3,400 IU a day in divided doses. As of 2009, the toxic level of Vitamin D had not been established. It was estimated to be 6,000-8,000 IU, but this seems to me to be more of a guess. A physician friend of mine takes 6,000 IU daily. Vitamin D may have profound beneficial effects on the nervous system and cardiovascular system. We know it helps with preventing osteoporosis. That literature is extensive.

Do you need supplemental vitamin D? The only way to know is to have your doctor do a Vitamin D level on you. It is a simple blood test. My internist gets a Vitamin D level on me every two years.

Sunscreen Ingredients

Here's a list I found on the Internet.

A chemical block has the ability to be absorbed by the skin, sunlight is rendered nil or invalid upon contact.

A physical block sits on the skin's surface and does not have the ability to be absorbed into the skin. Light is either absorbed into the sunblock material or reflected away from the body back into the atmosphere similar to a mirror or tin foil.

The information provided in these patient information sheets is offered for general informational and educational purposes only; it is not offered as and does not constitute medical advice. In no way are any of the materials presented meant to be a substitute for professional medical care or attention by a qualified practitioner, nor should they be construed as such.

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