But this ratio may lead to a false sense of security since studies have shown that people using a higher sunscreen tend to stay 20 % longer in the sun which is not necessarily the intention of sunscreen.
Facts about sunscreen and its use
Since UVA and UVB can cause irritation, photoaging, or cancer of the skin, you need to protect your skin from these harmful rays. One way to protect your skin is the use of sunscreen. There are some important facts you need to know about sunscreen to get the maximum protection they can provide.
But still always keep in mind that sunscreen should not be your first choice of protecting your skin from UV radiation since it does not provide complete protection. The best protection against sun related skin damage is to stay out of the sun.
We are well aware that staying out of the sun entirely is an impossible task and also not healthy but whenever you go outside avoid midday sun, seek shade and use a sunscreen.
Different kinds of sunscreen
Most often you will find sunscreen in the form of sun milk. Milk is a liquid emulsion. Most common is a oil-in-water emulsion. But sunscreen can also come in the form of cream, oil, or a water based gel.
A sunscreen needs ingredients to filter UVA and UVB. The problem with some of these ingredients is that they are not neccessarily photostable which means they will lose their ability to protect against UV radiation after a while in the sun. Therefore sunscreens have to be replenished by stabilizers which may induce allergic reactions.
Basically there are two different concepts of protection:
Physical protection such as mineral pigments that reflect the sun light
The problem with mineral pigments is that they apply with a white color that will possibly disappear after a while. But there is also a positive aspect to this which is that you have a visual control where you have already applied sunscreen and where you may have missed a skin area. If you know that you are allergic to chemical UV filters (see UVA and UVB filter) you should consider using a sunscreen with micropigments since they do not penetrate the skin like chemical filters but lay on top of the skin and reflect the sun light. But if used alone i.e. without a chemical filter micropigments have been shown to provide poor protection against UVA radiation.
Mineral Pigments or Micropigments
- titanium dioxide
- zinc oxide
Chemical protection which absorbs UV radiation
- butyl methoxydibenzolmethane (dibenzolmethane)
Is often used to filter UVA but which is known to be very unstable.
- thylbenzylidene camphor
Is used to filter UVB and in addition functions as a stabilizer for the UVA filter.
- yl triazone/ octocrylene
Is also used as a UVB filter and has the ability to stabilize the UVA filter.
- yl methoxycinnamate
The Sun Protection Factor (SPF)
The SPF is the ratio of the time required to produce minimal erythema on skin covered by a sunscreen product to the time required to produce the same degree of erythema without the sunscreen. If you usually turn red after 10 minutes unprotected in the sun and next time you use a sunscreen with SPF 15 you can stay 150 minutes in the sun without getting a sunburn. But this ratio may lead to a false sense of security since studies have shown that people using a higher sunscreen tend to stay 20 % longer in the sun which is not necessarily the intention of sunscreen.
Use a broad spectrum sunscreen of at least SPF 15
Always have in mind that both UVA and UVB are considered to have a negative impact on our skin and are responsible for irritations, aging and skin cancer. Because of that you should use a broad spectrum sunscreen which protects you from UVB AND UVA. Sunscreen should become a part of your daily skin care program since UV radiation also exists on cloudy days. To block as much radiation as possible use at least a sunscreen with SPF 15. SPF 15 blocks about 93% of harmful UV radiation whereas SPF 30 blocks about 97% of UV radiation. At present, many of the normal beauty products contain sunscreen.
In general a sunscreen is considered to be waterproof when about 50 % of its filter effectiveness remains after having been in contact with water.
Reapply often and use a good amount of sunscreen
Clinical studies revealed that most people do not use sunscreen properly: they do not apply enough of it. For an average body you need about 35 ml (~1 1/4 fl. oz.) of sunscreen.
Always apply sunscreen half an hour before you expose yourself to the sun. Reapply every two to three hours. Do so even when you are using a waterproof sunscreen. This is because most of the ingredients of a sunscreen form unstable compounds that will fall apart after a certain amount of time and light doses. They also can rub off, sweat off, or wash off. But be aware that reapplying does not increase the SPF!
Where to use sunscreen
The general rule should be that you cover every part of your body with sunscreen that might be exposed to sun light. Certain parts of your body have a special risk of getting burned since they are more exposed areas of your body than others. These so called sun terraces are:
- bridge of the nose
- lower lip
- top of the ear
- outside of the arms
- back of the hands
While sitting you should also protect your upper leg.
Supposedly negative aspects of sunscreen
We certainly do not want to unsettle you but we have to call attention to the fact that several epidemiological studies lead to the assumption that sunscreen may even increase your skin cancer risk. There are some explanations how this statement can be illustrated and put in perspective:
- Lack of UVA protection in sunscreens
The discovery that UVA may also be responsible for inducing skin cancer is rather new. It is only since this time that the sunscreen industry has started producing broad-spectrum sunscreens that will protect your skin from both UVA and UVB radiation. But bear in mind that these studies were done with people who had basically used sunscreen that contained only UVB protection.
- Wrong application of sunscreen
Studies revealed that most of the people who use sunscreen do not use it properly. They do not apply enough of it and do not reapply it regularly. Therefore the protection they can provide is not fully exploited. You need at least 1 1/4 fl. oz. of sunscreen for your body. Apply it evenly and reapply every one to two hours.
- Prolong time spent in the sun
The use of sunscreen may lead to a change in tanning behavior. People consider themselves safe when they use sunscreen and stay in the sun even longer. Sunscreen protects you to some extent, but it is not a license for excessive sun exposure.
- Previous sun exposure
The time one has spent in the sun can be a clue as to whether somebody is at high risk of developing skin cancer or not. But estimating of previous sun exposure is a difficult task since nobody can exactly count the hours he or she has ever spent in the sun.
- Use of sunscreen by those at high risk
Another possible source for flaws to the main claim of this whole section is the fact that sunscreen is mainly used by people who tend to burn easily and these are the people who are at high risk for developing skin cancer anyway.
Overall there is no certainty about the assumption that the use of sunscreen may increase the risk of getting skin cancer. So do not stop using sunscreen. It is still important to protect yourself from UVA and UVB radiation. Just make sure you use it properly and avoid excessive sun exposure.
Again sunscreen is great, but it should not be your main defense against the harmful rays of the sun. Sunscreen should complement your protection against the harmful rays of the sun.
Next to sunscreen you should do the following to protect yourself:
- TEN TO FOUR… SUNLIGHT NO!
Try to stay out of the sun between 10 a.m. and 4 p.m. This may be unrealistic for some, so try to postpone sun intensive activities (like swimming) for the late afternoon and early morning hours and seek shade.
- If you do not have a watch use the shadow rule: if your shadow is shorter than you… head for cover.
- Be sure to wear protective clothing, which for some may be more realistic than avoiding the sun totally.
- Do not be fooled by the clouds (most UV light penetrates the clouds).
- Water? Snow? Be especially careful, both reflect the harmful rays of the sun (it can cause some funny looking sun burns in strange places). When around reflective surfaces like snow and water use sunscreen (even under your nose, on your chin, on the bottom of your ears…)