What is a sunscreen?

Sunscreens come as lotions, creams, ointments, gels, liquids, sprays, sticks, and films. What they all have in common is that they contain at least one substance that has the capacity to reduce the amount of potentially dangerous ultraviolet light that passes through onto the skin. Whether the sunscreen chemical or chemicals reduce the amount of ultraviolet energy getting to the skin surface by blocking it, scattering it, or absorbing it, the end result is less damage to the skin.

What are the substances or chemicals that make sunscreens effective?

The FDA has a list of chemicals that can safely be used for formulating a sunscreen. These include padimate O, homosalate, octyl methoxycinnamate, benzophenone, octyl salicylate, phenylbenzimidazole sulfonic acid, octocrylene, oxybenzone, avobenzone (Parsol 1789), Mexoryl, titanium dioxide, and zinc oxide. In the judgement of the FDA all of these chemicals are safe to use in the concentrations that the FDA specifies. If a drug company wanted to market a sunscreen with a sunscreen chemical not on this list, it would have to go through a complete drug approval process just as if it were developing any pharmaceutical product.

Because each of these chemicals provides slightly different layers of protection, many sunscreens contain combinations of chemicals in order to either enhance the protection or reduce side effects like stinging.

Sometimes you will see some proprietary names like Helioplex. These names are not the actual chemical ingredients, but rather represent special formulation processes to enhance the sunscreen by overcoming some disadvantage of one or more the the FDA approved chemicals. For instance, avobenzone (Parsol 1789) breaks down when exposed to ultraviolet light and becomes progressively less effective over time. Helioplex is designed to stabilize avobenzone (Parsol 1789) and thereby make it last longer when exposed to ultraviolet light.

What is the best sunscreen to use?

It depends.

Fortunately, there are many excellent, as well as different, sunscreen products today. The good news is that there is plenty of choice. The bad news is that there is plenty of choice.

I frequently suggest that patients approach this wide selection the same way they pick out clothes. When you buy clothes, you want something that looks good on you, is appropriate for the occasion, fits well, and is priced right. Pretty much the same rules apply in selecting a sunscreen. Moreover, most of us have different clothes – something for casual wear, something for work, something for special occasions, warmer clothes for winter, lighter clothes for summer. If you are serious about using sunscreens, you will probably need a few different ones – just like you need different clothes.

Some of the qualities of sunscreens that you should take into consideration include:

The Formulation

Those with sensitive skin may prefer ointments, creams, sticks, or lotions since they generally will not be as drying as gels, liquids, or sprays. Those with less sensitive skin may prefer the reverse.

If you have acne, oil free sunscreens are preferred. Many manufacturers use the term “non comedogenic” which literally means that it doesn’t cause white heads and black heads to form. This is a useful guide, but be forewarned. The way “non comedogenic” is determined is by applying the product to rabbit ears and then checking to see if bumps form. If you are not a rabbit, that test may not accurately predict how that sunscreen will affect you.

Studies show that most patients prefer sprays to other kinds of formulations. Sprays are quick to apply, easy to put on hairy areas, and generally offer good protection. But here is the problem: people tend to put sprays on too lightly and too unevenly. I recommend generous applications followed by using your hands to spread the formulation. On the face, I recommend spraying the formulation onto the fingers and applying rather than spraying directly on the face (since you may inhale it or get it in yours eyes). Sometimes using a non spray formulation works better on the face since you end up applying it anyway and therefore lose the convenience of a spray.

On young children sunscreens that remain white after applying (at least for a few minutes) help parents make sure that the coverage is complete.

Sticks work best on the lips and sometimes near the eyelids. They are also convenient to keep in a pocket for reapplication later.


SPF stands for sun protection factor. It is important to understand that SPF is a measure of UVB protection (UVB rays are the short ultraviolet rays which are primarily responsible for most sunburns and are important in causing all types of skin cancer.). The SPF tells you essentially nothing about UVA protection. UVA is the longest wavelength of ultraviolet light. It plays a role in increasing the risk of squamous cell carcinoma and melanoma. Because longer waves penetrate more deeply into the skin, UVA radiation is a significant contributor to premature aging of the skin.

All other things being equal (and they usually are not), the higher the SPF the greater the protection from UVB. But doubling an SPF factor does not double the protection. For instance, a SPF 30 sunscreen only provides 3% more UVB protection than an SPF 15. As a practical matter, beyond an SPF of 30 other factors often become more important – how much UVA protection is there?, how well does it stay on?, is it water resistant?, is it sweat resistant?

Because the SPF is measured by applying a sunscreen at a prescribed thickness, the actual SPF when you apply it to yourself may be less. The average person applies a sunscreen at one half the thickness (or less) required to achieve the stated amount of UVB protection. The implication of that fact is that when most apply an SPF 30, they are getting a much lower SPF.

But that may not always be entirely true. Why? Because even though all sunscreens are tested at the same thickness of application, some formulations provide the same protection at lesser thicknesses. The problem is that you and I do not generally know which ones those are. So, the best advice is apply a sunscreen at at least twice the thickness that you would normally apply another cream or lotion.

The FDA would do us all favor if it reconsidered its testing procedures to encourage companies to construct different products that could be applied more thinly and still provide the stated SPF rather than its current process which requires one size to fit all. Moreover, it would be very helpful if products had properties that helped make it clear how thickly they should be applied. For instance, suppose a sunscreen were formulated so that it “glistened” or produced a color prior to drying when applied at the optimal thickness. Alternatively, perhaps a sunscreen could have an applicator that measured just the right amount of sunscreen to apply. Before that time a useful guide is to apply a teaspoon of sunscreen to cover the face, two tablespoons to cover the entire body.

Sweat proof or sweat resistance?

How well a sunscreen stays on when perspiring is important for sunscreens used during sports activity or on warm days. Claims by manufacturers about being sweat proof or sweat resistant are, unfortunately, claims. There is no FDA approved measure to substantiate this claim. I think there should be. As a consumer, your best guide is your personal experience and reviews by independent sources such as Consumer Reports (www.ConsumerReports.org.) If you are interested in learning more about some of the inadequacies of current FDA guidelines, you might check out an article on that subject published in the New York Times in 2007 (www.nytimes.com/2007/07/05/fashion/05skin.html).

Water resistant and Very water resistant?

Obviously, if you are going to be swimming, a sunscreen that does not come off in the water is desirable. The FDA does have a measure, however inadequate, to help you determine how effectively a sunscreen stays on in the water. Prior to 2002 a sunscreen that stayed on for up to 80 minutes was called water proof. Now the term is very water resistant. The term water resistant means that the sunscreen has stayed on for forty minutes under FDA determined conditions.

Okay, so that helps. But FDA determined conditions are not necessarily the condition under which you will be using the sunscreen. What if you are getting in and out of the water? Will it still stay on just as well as continuous soaking for the same amount of time? What about in a hot tub? Does water temperature affect it? Or the pH of the water in a pool? Or what about salt water instead of fresh water?

In any case, the terms water resistant and very water resistant are nevertheless helpful guides. The bottom line: Reapply often and monitor how the sunscreen works for you under the conditions in which you use it. You might also consider getting some sun protective clothing to wear while swimming. At least if that comes off, you (and others) will notice.

Broad spectrum or UVA protection?

By now you have probably figured out that we have been talking mostly about protection from UVB rays. There is a good historical reason for this emphasis: only in the last decade or so have we come to appreciate the fact that UVA rays are medically important as well.

Part of this recognition came as a result of a well intended medical intervention gone bad – so-called PUVA. PUVA is medical treatment in which long wave ultraviolet rays (UVA) are enhanced by giving patient a psoralen chemical. Psoriasis, urticaria pigmentosa, and mycosis fungoides are three skin diseases that often benefit from this treatment. The good news is that it works for many patients; the bad news is that some develop squamous cell carcinomas and melanomas. What that taught us is that UVA is not as harmless as previously thought.

But that created another issue – sunscreens up to that point had concentrated on preventing UVB damage. Now it was clear that to be medically effective sunscreens needed to protect against UVA as well.

Again, the FDA has been slow to recognize this shift and provide consumer information about UVA protection (like the SPF which tells you about UVB protection). Manufacturers of sunscreens have attempted to fill this void by advertising their products as “broad spectrum” or “protects against UVA.” But those claims do not tell you how much protection is afforded by those products.

The good news is that the FDA has committed to providing something equivalent to the SPF within the next year. The bad news is that you are on your own until that time.

Though inadequate, here’s the best you can do to find a sunscreen with UVA protection. Look at the ingredients. The widest protection is generally offered by sunscreens that contain titanium dioxide or zinc oxide. After that the chemicals to look for in the label are avobenzone (Parsol 1789), mexoryl, or oxybenzone.

Do sunscreens cause cancer?

The evidence that sunscreens cause cancer is pretty questionable. You might want to check out at piece in the New York Times on that question (www.skincancer.org/sunscreen-safety-is-called-into-question.html). The chemicals themselves do not seem to convey an increased cancer risk, and clearly the benefit they convey reduces cancer risk.

But the real question is whether sunscreen use causes skin cancer. Here the answer is a little more complicated.

The problem is that sunscreens all have “holes.” None completely prevent entirely against all ultraviolet wavelengths under all conditions. So, when you wear a sunscreen, you are still getting ultraviolet damage.

The argument that sunscreen use may increase the risk of skin cancer goes basically like this: if you wear a sunscreen, you will stay out longer in the sun. You may not get a sunburn, but the “holes” in your sunscreen mean that you are getting more ultraviolet damage (at least for the wavelengths that gets through those “holes”) than if you had not worn sunscreen and spent less time in the sun.

The answer to that objection is to not use sunscreens as a reason to stay out longer; and when you do, make sure you use broad spectrum sunscreens (since the biggest “hole” is UVA protection).

Another argument is that sunlight (mostly UVB) acting on your skin produces Vitamin D which may have a protective effect against certain skin and internal cancers. If you use sunscreen, you will produce less Vitamin D, and therefore you will be more likely to get cancer.

The American Academy of Dermatology recommends (and so do I) that any adult using sunscreens on a regular basis take 1,000 international units of Vitamin D daily. This dose is basically harmless and is probably a good idea in any adult whether you use sunscreens or not (I take it). The American Academy of Pediatrics recommends 400 international units a day for each child beginning on day one. So, take Vitamin D internally (the D3 form is the most effective) and don’t worry about sunscreens producing cancer.

How do I prevent damage from the “holes” in sunscreens?

Recall that sunscreens work because they contain chemicals that either block, absorb, or scatter ultraviolet rays. Each chemical is slightly different in how that is done – meaning that each “leaks” at slightly different wavelengths. That “leak” or “hole” may also depend upon the formulation of the sunscreen so that even the same chemical in two different sunscreens may leak in two different patterns. This phenomenon is called a polar shift and is probably more than you wanted to know.

The point is that whatever sunscreen you use still lets in some damaging rays. How important that leakage is depends upon how much sun you are getting. If you are a commercial fisherman, it is probably very important. If you live your life mostly indoors, it may not be very important. For many who do not have outside occupations or who do not engage regularly in outdoor sports, there may be occasions where there is intensive sun exposure (like a week at the beach) where it is important but not the rest of the time.

There are three strategies for dealing with leaky sunscreens. First, try to substitute a physical block – like sun protective clothing. Second, sunscreens with zinc oxide or titanium dioxide tend to provide broader protection with fewer holes. Try a sunscreen with one of those ingredients. Third, use different sunscreens that contain different chemicals on different days. Presumably, the different sunscreens will have “holes” in different places, so by switching around you don’t just keep getting the same injury day after day.

I used a sunscreen and still developed a sunburn. Why?

There could be many reasons – the sunscreen could be out of date, you stayed in the water longer than the sunscreen was designed to stay on, perspiration washed the sunscreen off, you put it on too thinly to get the full effect, you got more sun than you realized because it was cool or you were in the shade, or you forgot to put on the sunscreen and don’t remember that you forgot. But none of those obvious reasons are the explanation that applies to most people who voice this complaint to me.

Most patients who complain that a sunscreen did not work have tried many sunscreens first and none of them work. No matter what they use, they burn.

I generally ask them four questions. How soon did the sunburn appear, did it itch, what medicines did you take before going into the sun, and when did the sunburn go away?

The most common answer to those questions is “It started right away, did not itch, was taking no medications, and was gone in a few hours or by the next morning.” That person did not have a “classic” sunburn – they were flushing. A “classic” sunburn is caused by UVB rays. It begins several hours after exposure, reaches its peak 24 hours later, and then gradually improves over days. Most sunscreens are effective at preventing this “classic” sunburn. Bottom line: if the redness is gone by the next morning, you can be sure the sunscreen worked.

Flushing is harmless, and the most important reason for realizing that the immediate redness after sun exposure is flushing and not a burn is so that you don’t give up on wearing sunscreens because you assume that they do not work on you.

While sunburns can itch – especially when healing, severe itching may suggest an allergic reaction, perhaps to the sunscreen. Most common allergic reaction to sunscreens are limited to the area where the sunscreen was applied, worsen for several days, and may take one or two weeks to fade unless treated.

Finally, medication reactions or redness because of photosensitivity disease such a polymorphous light eruption also tend to itch and persist. Again, these causes do not represent sunscreen failure per se.

Is it really necessary to reapply sunscreen every 2 hours?

Maybe not, but it’s probably a good idea.

Reapplying sunscreen every two hours has become part of the popular lore of sunscreen rules that everyone should follow even though it represents an oversimplification.

Some sunscreens under some conditions will come off sooner and some later than two hours. Moreover, it is an act of faith to assume that reapplying a sunscreen on top of a previous application is as effective as washing off the previous application first. Makers of sunscreen products are not required to show that reapplication results in the same effectiveness as the original application.

But in the face of our collective ignorance, reapplying every two hours when getting significant sun exposure is a good idea. If you have been swimming or heavily perspiring, forty minutes might be a better reapplication time. One suggestion, however, is that I would recommend reapplying the same sunscreen as was applied previously. When you start mixing sunscreens on your skin, you are creating an entirely new formulation which may be much less effective than you think. Adding an SPF 30 to an SPF 15 does not make a 45 – it might make a 3.

Should I put on my moisturizer before or after I put on my sunscreen?

Neither. It is better to buy a sunscreen in a moisturizing base than to mix two different products on the skin. Again, the reason is that sunscreens are complex formulations. Mixing two different sunscreens together or mixing a sunscreen plus a moisturizer is like putting together the ingredients for a chocolate cake with the ingredients for creme brulee and then expecting that it will make a nice chocolate creme brulee after it is baked.

How important is it to apply sunscreen at least one half hour before sun exposure?

Probably not.

The half hour idea started over forty years ago when the most effective sunscreens were made by dissolving PABA in alcohol. There was some evidence to believe that it took that preparation half an hour to reach full benefit. Then when the FDA first designed the rules for determining SPF, it specified that the sunscreen should be applied half an hour prior to testing the sunscreen.

The likelihood is that many of our modern sunscreen chemicals start working immediately upon application. But we just do not know because makers of sunscreens are not encouraged by the FDA to test different application schedules.

So, the bottom line is: if you can apply the sunscreen one half hour before exposure, do it; but if you can’t, apply it anyway.

It says on the sunscreen not to apply to a child under the age of six months. How do I protect my three month old from sun damage?

The American Academy of Pediatrics says its okay to apply sunscreen before the age of six months on a carefully limited basis, and I agree. But there is a much more important issue – an infant should not generally be in a situation where sunscreens are needed.

If an infant is going to be outdoors, follow the non-sunscreen suggestions for a sun protection program first – avoid middle of the day exposure, cover with appropriate clothing including hats, stay out of direct sunlight as much as possible, avoid areas where there is a high reflectance of ultraviolet light (such as the beach or in a boat), and then use sunscreen as a last resort on limited exposed areas.

What are the best sunscreens for children?

Sunscreens for adults work fine on children, and sunscreens for children work fine on adults.

With children there are some special considerations, however. But let me start with some general advice – don’t expect your child to be very excited about wearing a sunscreen if you or your spouse don’t wear one.

The first challenge is to find a sunscreen that has some appeal – maybe the color of the container, a picture on the box it comes in, its smell, how it feels, maybe its presentation as a game, maybe the action of a spray, or the feel of a cooling gel. It’s just like meal time. Some foods you have to be somewhat firm and perhaps coercive about eating, but others they like. If you can win the battle with something they like, you are there.

In general, children have more sensitive skin than adults so lotions or creams may feel better or bother their skin less. On the other hand, some children like sprays and dislike creams. Go figure.

Products that you can see where they are on the skin are a plus in making sure you are getting complete coverage.

Fragrances can be appealing to a child – making it easier to get them to use the product. But fragrances are also appealing to insects. Fragrance free products, especially in children sensitive to insect bites, are a plus.

In very young children, I used to recommend formulations with either zinc oxide or titanium dioxide since these are largely inert, non-irritating chemicals that provide good broad spectrum protection. But questions have now been raised about using them since modern formulations usually are made with ultrafine particles called nanoparticles. The concern is that these very fine particles might be inhaled and cause a lung problem later. I think that possibility is very unlikely since the particles are in cream, ointment, or lotion. Based upon our current knowledge, there is no reason not to use them in children. But the argument for preferring them over other products is much weaker.

Sometimes using one of the stick formulations on the face around the eyes can be easier to apply to a moving target without getting the sunscreen the eyes. Also, in general, they tend to remain in place during rubbing and perspiration and thereby cause less stinging in the eyes.

Finally, while on the subject of stick formulations, don’t forget to protect the lips. Stick formulations work best there.

The Center for Disease Control has a short PDF on sun protection in children that might prove useful. www.cdc.gov/cancer/skin/pdf/CYCParentsBrochure.pdf

Is there a certain age at which it is not important to use sunscreen anymore?

Yes, but it is not just a matter of age but of what you are doing, your history of skin cancer, and your life expectancy.

Many of my older patients point out that the damage was done years ago and ask if there is any point in continuing to use sunscreens. While it is true that much of the damage was done years before, there are still good reasons to keep using them if one still has a few years left and enjoys the outdoors.

First of all, it is entirely possible that some of the damage from years ago can be undone by following a good sun protection program. Clinically, I have seen this happen in many of the patients I have followed over the years, especially when the more highly effective sunscreens became generally available.

Second, classically we have thought of cancer development as proceeding in two stages--initiation and promotion. Initiation is the planting of the seeds. That is the damage that was done years ago. Promotion is the watering and fertilizing of the seeds to encourage them to sprout. Ultraviolet radiation is both an initiator and a promoter. So, even though the seeds may still be there, it makes sense not to encourage them to grow.

Do sunscreens become less effective over time?

In general, yes.

Ideally, a sunscreen product should have an expiration date on the package. If not, I recommend not using a product that is more than a year old.

A nice, but more technical review, on sunscreens can be found at www.medscape.com/viewarticle/580643_5.

A less technical but good review of sunscreens can be found at www.skincancer.org/sunscreen/.

The Mayo Clinic has another well-written piece on sunscreens as well.

Back to Top

Precancerous Skin

Visible light consists of many different wavelengths which are generally “mixed together” – so-called white light. When these wavelengths are split into “layers” by the prism effect of moisture in the atmosphere, the colors of different wavelengths are revealed and we see a rainbow. The shortest wavelength is at the bottom of the rainbow and produces the color violet. Below that wavelength the rainbow becomes invisible and seems to disappear. We call that invisible layer ultraviolet. It is the ultraviolet part of light energy that causes skin cancer and premature aging of the skin. Ultraviolet is the part of the rainbow that we cannot see with our eyes.

Ultraviolet Protection

Ultraviolet rays are a form of energy that comes from the sun. Without ultraviolet light life would not be possible. All of our plant life depends upon it. Ultraviolet light acts on our skin to produce vitamin D. But ultraviolet energy can also be harmful. Like visible light in which different wavelengths produce different colors, different wavelengths of ultraviolet produce different biologic effects--both good and bad.

Sunscreen Skin Protection

The three major groupings (or “layers”) of ultraviolet wavelengths are called UVA, UVB, and UVC. Fortunately, all UVC (which is the shortest ultraviolet wavelength) is screened out by our atmosphere. If it were not, it would make life on earth impossible by killing the life forms that make human existence possible. The next shortest wavelength, UVB, is only partly screened out by the atmosphere. UVB’s bad effects include sunburns, skin cancers, and premature aging of the skin. Because it is only partly screened out by the atmosphere, it is most intense in the middle part of the day when the sun’s rays do not have to penetrate as thick an atmospheric layer as they do early in the morning or late in the evening. That is why walking on the beach early in the morning is less likely to produce a sunburn or sun damage. UVA is the longest ultraviolet wavelength and is minimally screened out by the atmosphere. UVA is associated with increased likelihood of premature skin aging, squamous cell carcinomas, and malignant melanomas. It is just as intense from sunrise to sunset. Thus, the most important sunscreen of all is the atmosphere. It completely blocks UVC, partly blocks UVB, and doesn’t block significant amounts of UVA. You don’t have to apply it, and it is free.

UVA UVB Damage

Things that block visible light, like clouds or fog, do not always block the invisible ultraviolet light. That is why you can get a sunburn on a cloudy day or sitting in the shade.

Melanoma Prevention

There are many things that function to screen or reduce ultraviolet rays--the atmosphere, window films, chemicals applied to glasses, even untreated window glass. Untreated glass effectively screens out most UVB (but not UVA). That is why you don’t get a sunburn while riding all day in a car or while sitting inside by a window. But, in general, when talking about sunscreens, we are referring to products applied to the skin for the purpose of reducing the amount of ultraviolet damage.

Ultraviolet Light Radiation

Sunscreens come in many different formulations and delivery systems. The trick is to match the ideal formulation and delivery system with your skin type, activity, amount of ultraviolet exposure, individual skin sensitivities, special needs, and preferences. There is no such thing as the “best” sunscreen for every person, for every part of the body, and for every situation. If you want to be really serious about sunscreen use, you probably will need several different sunscreens.

Sun Protection

Sunscreens formulated for children are fine to use on adults. Sunscreens formulated for adults are fine to use on children. Reputable manufacturers try, however, to provide some guidance about the special properties of each formulation to help you select a product best suited for your needs. The only claims that have been standardized by FDA regulation are the SPF number (which measures UVB protection only) and the degree of resistance to wash off in water. All other claims--tear free, doesn’t sting eyes, non-irritating, broad spectrum, protects against UVA, sweat proof, sweat resistant, ultra sweat proof, gentle, mild, hypoallergenic, or whatever – are based upon the manufacturer’s own criteria. Those claims are guidance, not guarantees. The only way to know how they work on you is to try them.

nodular melanoma

Sunscreens come in lotions, creams, ointments, gels, sticks, and sprays. Each formulation has advantages and disadvantages. Lotions can be anything from a liquid with an alcohol base to a thick creamy liquid and are packaged to encourage direct application with the hands or to be sprayed or rolled on. Sprays tend to be quicker and easier to apply – especially to hairy areas. In actual practice I am not so sure that the convenience of a spray doesn’t encourage missed areas and uneven application. But one can be careless with direct application formulations as well. In the end, it all comes down to diligence. On the face I recommend that a spray be squirted onto the hands and applied to avoid getting it into the eyes and to encourage more even coverage. On other body areas, I recommend a thick spray and then spreading it with your hands.

Tampa Dermatology

Many forget to protect their lips with sunscreen. That oversight is too bad because skin cancer on the lip tends to be more serious and require more aggressive treatment. Sticks are nice for lips. In general, I prefer formulations that do not have a lot of “stuff” added. Simple is better. Some patients also like stick formulations for applying near the eyelids and on the ears. They fit into pockets so they are easy to carry along for reapplication.


Skin Cancer Prevention

How a sunscreen is applied may be more important than the one chosen. Most people apply a sunscreen too thinly and do not get its full benefit. Many forget or ignore important areas like the ears and lips. Carefully apply thickly to all exposed skin (except eyelids which are best protected by glasses with ultraviolet protective lenses) prior to sun exposure and when the skin is dry. While the general recommendation is to apply sunscreen one half hour prior to exposure, that advice is probably misleading, and it is more important just to apply it – if only minutes before. While the optimal thickness of application of any individual sunscreen is not known, a general rule of thumb is that it takes about a teaspoon of sunscreen to cover the face, two tablespoons to cover the body.