UV radiation

How does it work and how do we use it wisely?
UV radiation

Spring is coming. With the first spring days, also come the first rays of sunshine. The sun feels great, it gives people a good feeling. Small amounts of UV rays are needed for the production of vitamin D in our skin. But the wonderful rays of the sun are insidious; the UV light in the sun is harmful to us. We cannot stay in the sun without any protection. In the short term, too much exposure to sunlight leads to sunburns. In the longer term, excessive sun exposure leads to skin aging and sometimes skin cancer. Exposure to the sun is a cumulative risk. People who frequently stay in direct sunlight will suffer sun damage over time. Skin cancer occurs in people who spend a lot of time in the sun for work. But the average Dutch person also gets skin cancer more often. In the last 10 years there has been an explosive increase in the number of skin cancers. Skin cancer can be treated well in most cases, but not in some cases. Every year 900 people die in the Netherlands as a result of a melanoma, the most malignant form of skin cancer. The increase can be explained by an increase in sun exposure during winter and sun vacations and through the use of sunbeds. Children are more exposed to sunlight as well. Protection against excessive sun exposure is of great importance. The skin naturally has sun protection, but to support this protection it is strongly recommended act wisely. For example, it is advisable to use sunscreen when exposed to the sun. Unfortunately, in practice we often see that many people do this badly. By not putting on enough sunscreen, or not often enough, you are not getting the desired protection against UV damage. To understand how anti-sunburn products work and how to best protect yourself against excessive sun exposure, we first have to delve into sunlight, skin type and UV index.

What does sunlight consist of?

The sun gives off infrared radiation, visible light and UV radiation. The infrared radiation is invisible and gives us warmth. The visible light gives plants energy for photosynthesis and determines the biorhythm of people and animals. Ultraviolet radiation (UV radiation) is also invisible. UV radiation is subdivided into three types: UVA, UVB and UVC radiation. All three types can be harmful to the skin. Excessive exposure to UV radiation can pose a health hazard. Too much UV radiation damages the skin cells, causing burns and redness. The skin can usually repair the damage itself, but in some cases that goes wrong. In the long term, the effects of excessive UV exposure are skin ageing and skin cancer formation. Skin ageing can be seen in wrinkles, pigmentation spots and sagging skin. 90% of skin ageing is caused by sun damage. Ultraviolet irradiation of the skin is the main preventable cause of all forms of skin cancer: melanoma, basal cell carcinoma and squamous cell carcinoma.

What is UVA radiation and what does it do?

UVA radiation is present in sunlight all year round. So also in fall and winter. UVA radiation is not properly blocked by the clouds. It is also not completely blocked by glass. Glass transmits 70% of the UVA radiation, so even behind glass you are not protected against the sun! UVA radiation has a long wavelength. As a result, it penetrates deep into the skin, where the DNA of vulnerable skin cells can be damaged. This can lead to skin cancer over time. UVA radiation also affects the collagen and elastin in the dermis. Collagen and elastin ensure the firmness and suppleness of the skin. Long-term damage to this leads to accelerated skin ageing due to sagging skin. UVA radiation on the skin does not cause burns. As a result, the skin does not receive a warning signal in the event of excessive exposure. You do not see that this radiation is active in the skin and therefore it is dangerous. UVA rays make the skin tan. This happens relatively fast, because UVA rays change the existing pigment in the skin. This is the so-called direct pigmentation. This brown discoloration only lasts a few hours and provides little protection.

What is UVB radiation and what does it do?

UVB radiation is mainly present during spring and summer. This radiation causes us to tan, but, without protection, also to burn. Glass only transmits 10% of the UVB radiation from the sun. The UVB radiation only reaches the upper layer of the skin, the epidermis. Here, UVB radiation causes the tanning or burning of the skin. The epidermis protects itself against UVB radiation by getting thicker. The cells in the epidermis begin to divide faster under the influence of the UVB rays. This causes the epidermis to thicken and to form a shield that reflects the sunlight. There are melanocytes in the epidermis. These cells play an important role in the tanning of the skin. Under the influence of UVB radiation, these cells produce a brown substance called melanin. Melanin is spread in the epidermis, making the skin brown. Melanin is able to absorb part of the UV radiation and thus protect the vulnerable living cells of the basal layer against UV radiation. The brown pigment forms a protective layer above the basal layer. The skin tries to protect itself against the harmful effects of excessive exposure to UVB radiation. This self-protection of the skin, however, is only a low protection against UV radiation, maximum SPF 5. SPF stands for Sun Protection Factor. We will come back to this later. Tanning is a protection reaction of the skin: if the skin has turned brown, then it has already been damaged! Too much UVB radiation causes a red color or burnt skin. Sunburn plays a major role in the development of skin cancer.

What is UVS radiation and what does it do?

UVC is the most powerful and the most dangerous form of radiation. Fortunately, this type of radiation is completely blocked by the atmosphere. The ozone layer plays an important role in this. UVC can weaken our immune system and is highly carcinogenic. Normally it does not reach the earth, but due to the known hole in the ozone layer, it can eventually pose a danger to public health.
Below you can see an overview of the effect of UVA and UVB radiation on the skin.

UV effects UVB UVA
Thickening skin yes no
Pigmentation yes yes
Vitamine D yes no
Burning yes no
DNA damage yes yes
Skincancer yes yes

What is a skintype?

Not every person responds to exposure to ultraviolet light to the same extent. How the skin reacts depends on the skin type. Your skin type is hereditary and does not change during life. There are six different skin types.

Skintype 1 Skintype 2 Skintype 3 Skintype 4 Skintype 5 Skintype 6
Burning experience Burns very quickly Burns very quickly Burns less quickly Burns almost never Very resistant to the sun Very resistant to the sun
Tanning experience Doesn’t tan Tans slowly Tans easily Tans very well Tans very well Tans very well
Appearance Very light skin.

Often freckles.

Red or lightblond hair.

Light eyes.

Light skin.

Blond hair.

Light eyes.

Light tinted skin.

Darkblond to brown hair.

Rather dark eyes.

Mediterrean type. Asian type. Negroide type.

Skintype 1

This skin type always burns and does not turn brown. People with this type have very light skin, usually with freckles on areas exposed to the sun, such as face, neck, décolleté and forearms. They also often have red or light blonde hair.

Skintype 2

This skin type usually burns and turns a little brown. The skin is also light in color. People with blond hair and gray, green or blue eyes often have skin type 2.

Skintype 3

This skin type rarely burns and tans well. The skin is slightly tinted. These people have dark blonde or brown hair and fairly dark eyes.

Skintype 4

This skin type almost never burns and tans well. This type is also called the Mediterranean type, because people in subtropical countries and people living around the Mediterranean Sea in particular have this skin type. The skin is more tinted and the people have dark hair and dark eyes.

Skintype 5

This skin type almost never burns and becomes deep brown. This type is also called the Asian skin type. These people have dark-stained skin or brown-yellow skin, black hair and dark eyes.

Skintype 6

This skin type never burns and is very dark brown or black. This is the black skin type. This skin type occurs in people who live in Africa or who have an African descent. People with skin type 6 have natural protection against sunburn.

People with fair skin who get sunburns easily have a greater risk of developing skin cancer than dark people with a lot of pigment in their skin. Approximately 39% of all Dutch people have skin types 1 or 2. Table 1 summarises the skin types and their characteristics.

You can determine your skin type at www.kanker.be/kankerpreventie/slimmer-de-zon/


The UV index is a measure of the amount of UV radiation that reaches the earth’s surface. The UV index in the Netherlands varies between 0 and 10. 0 is no UV index, 1-2 is virtually none, 3-4 weak, 5-6 moderate, 7-8 strong and 9-10 very strong UV index. The height of the sun determines the power of the sun. The higher the sun is, the stronger the sun power. The height of the sun depends on the season, the time of day and the place on earth. The distance that UV rays have to travel through the atmosphere is the shortest in the afternoon, when the sun is directly above us. In the Netherlands, the sun’s power is strongest between 12.00 and 15.00. In the summer the sun power in the Netherlands in the afternoon is a maximum of 6 or 7; in the winter often less than 1. In the tropics the season makes no difference. The closer to the equator, the stronger the UV radiation and the less the seasons differ. The higher you go (for example, in the mountains), the stronger the UV radiation is.

Clouding, reflection and the ozone layer

Not only the height of the sun, but also the thickness of the clouds, the degree of reflection and the thickness of the ozone layer play a role in the UV index. Hardly any UV radiation comes through a heavily cloudy sky with a thick cloud cover. In hazy weather, that is, a thin, misty cloud cover, a lot of UV radiation still reaches the earth’s surface. UV radiation is reflected by a wall, the sand and the water. This can amount to as much as 10 to 20% UV radiation. Under a parasol on the beach, or next to a wall or water, people are not fully protected. The reflection through fresh snow and ice is even 80 to 90%. The thinner the ozone layer, the less UV radiation is retained and the stronger the sun’s power. The ozone layer is thinnest over New Zealand and Australia. Skin cancer has taken on epidemic forms on this continent.
People with a light skin type burn more easily than people with a dark skin type. How quickly you burn also depends on the UV index. The calculation below shows how you speed up can burn an unprotected skin for any skin type.

  • Skin type 1: 67 minutes / sun power.
  • Skin type 2: 100 minutes / sun power.
  • Skin type 3: 200 minutes / sun power.
  • Skin type 4: 300 minutes / sun power.

Use sunscreen from UV index 3!

Tips for sunbathing

Now that we know what UV radiation is, how you can determine a skin type and how the UV index determines the speed of burning, we look further at how we can sunbathe wisely.
As stated, too much UV radiation can cause damage to the skin, such as short-term burns, accelerated skin ageing in the long term and a greater risk of skin cancer. The advice is: enjoy the sun, but make sure you don’t burn. Put on sunscreen, cover your skin, find the shade! But even if you do NOT burn, the skin will be damaged. SO ALWAYS PROTECT YOURSELF FROM THE SUN.


Sunscreens are made to protect the skin against sunburn and ageing. They contain UV filters so that less UV radiation reaches the skin. Sunscreen is an additional measure, besides wearing protective clothing, sunglasses with UV resistant glasses and finding the shade on sunny days. A sunscreen product is only adequate if the correct protection factor has been chosen, if the product has been applied in time, if you put it on frequently and use sufficiently.

What is sun protection factor and how do I choose the right one?

The degree of protection against UVB radiation is indicated with SPF; sun protection factor. Protection against UVA radiation is represented by a symbol with UVA in a circle. Protection against UVA radiation is represented by PPD (persistent pigmentation darkening). According to the new legislation in Europe since 2006, the protection against UVA radiation must be at least 1/3 of the protection against UVB radiation! There are chemical and physical filters. A physical, or mineral filter, forms a shield on the skin which reflects the sun’s radiation. These filters work immediately after applying. A disadvantage is that these filters are easy to wipe and leave a white haze. Chemical sunscreens or absorbent filters penetrate the skin. There they absorb the UV radiation from the sunlight. These filters stay in place better. Because these filters must be in contact with the skin for a while before they work, they must be applied half an hour before sun exposure in order to function optimally.

What Skin Protection Factor should you use?

Which SPF you should use depends on your skin type. SPF delays sunburns. Suppose an unprotected skin burns after 10 minutes. If you use a sunscreen with SPF 30, then the skin will burn after 300 minutes (10 minutes times 30 SPF). To achieve the correct SPF, you must apply a sufficient amount.

It has been calculated that 2 mg of cream per cm2 must be applied in order to get sufficient thickness. The image below shows how much that means.

For an adult this means that 35 g per application must be used. For a child it is 20 g per application! The cream must also be spread evenly over the skin and spread well. Most people only use 25-50% of the required amount. If half of the required amount of factor 50 is applied, only a quarter of the protection factor remains. Do not use spray because then you do not apply it thick enough. No sunscreen has a UVA and UVB filter that is stable in the sun and can withstand sweating and friction. The operation of the filters decreases after application. The speed at which this happens depends on the skin type, the strength of the sun and the filter used. So remember that in order to achieve the right SPF, you not only have to apply a sufficient amount, you also have to repeat the application every 2 hours. Application needs to be even more frequent during perspiration and after swimming.

Don’t forget the vulnerable parts

The lips, the nose, the skin around the eyes and the edges of the ears are sensitive areas. Long-term excessive exposure to UV radiation can cause damage in these areas, so don’t forget to apply sunscreen there! The backs and shoulders are often forgotten as well. Follow a fixed ritual to apply sunscreen to yourself or your (grand) children.

Choose a protection factor that matches your skin type and UV index. For skin type I an SPF of 20-30 applies in the Dutch sun, for skin type II: SPF 15+, for skin type III: SPF 15+ and for skin type IV SPF 10-15 is sufficient.
If you really want to sunbathe or go on vacation to an area with a high UV index, take a higher factor!

100% protection doesn’t exist

A sunscreen that stops all UV radiation does not exist. Even products with the highest factor cannot offer complete protection. Protection is provided by the absorbing capacity of the chemical filters and by the reflecting capacity of the physical filters. The table and drawing below shows how much UV radiation is absorbed or reflected.

  • SPF 2: 50% protection.
  • SPF 4: 75% protection.
  • SPF 8: 87.5% protection.
  • SPF 15: 93.3% protection.
  • SPF 30: 96.7% protection.
  • SPF50: 98% protection.

Waterproof doesn’t exist anymore!

Waterproof is a misleading claim that may no longer be used in Europe. A protection factor decreases after contact with water. The product must be reapplied after swimming and perspiring. Water resistant means that a product stays on better during contact with water. The disadvantage of these products is that they are very greasy and unpleasant to use because they stick more. Greasy sunscreens can also cause pimples. Sunscreens can be stored for approximately one to two years after being purchased at the store. After the package has been open or has been in contact with high temperatures, the factor on the package may decrease to a lower protection factor (SPF). The product then no longer provides full protection. All sunscreens on the Dutch market must comply with EU guidelines. There has been a lot of media attention for studies that assume that sunscreen products would not be safe or that they could even cause cancer. The Dutch Food and Consumer Product Safety Authority sees no reason to doubt the safety of sunscreen products in stores.

Thanks to Dr. Annemie Galimont-Collen, Dermatologist dermaTeam Middelburg, Goes and Zierikzee (the Netherlands).

Annemie Galimont was trained as a dermatologist at the Leiden University Medical Center. During her education, she was involved in the training of nurses and doctors. After her education, she established multidisciplinary expertise centers for skin cancer and wound care in Zeeland and the children’s eczema center “SMEER’M”. Since 2012 she has had a training company. Skin training provides tailor-made training for doctors, pharmacists, pharmacist’s assistants, nurses, skin therapists, bandagists, beauticians, and foot care providers. The courses are personal, small-scale and focused on daily practice.

Dermatologist Annemie Galimont has many years of expertise in providing information and training to patients and care providers and has also written brochures for patients, which can be found on skin doctor. In addition, she is a pioneer in multidisciplinary collaborations, a quality where we have a great need in the multi-disciplinary domain. Annemie involves healthcare providers in network collaborations, with an eye for and appreciation for everyone’s expertise and role. This creates well-functioning and future-proof networks.

For the Dutch Journal for Skin Care, Annemie Galimont writes articles in which the multidisciplinary powers and values of the many professionals in skincare are given a place.

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