The sun

The Sun is our closest star at a distance of 149 million kilometers from Earth.
It radiates electromagnetic waves (called solar radiation) which is essential to life.
However, its radiation can have a negative impact on the body.
Human beings are only exposed to a small part of this radiation as different layers in the Earth's atmosphere block out the most harmful rays.

Solar Radiation

The ozone layer in the stratosphere blocks the most dangerous radiation, including cosmic, UVC, gamma and X-rays. This prevents them from reaching the Earth's surface. In this way, the ozone layer acts as a shield against the sun's most harmful rays.

The following rays reach the Earth's surface:

  • UVB (280 to 320 nm) are the most dangerous rays that reach the Earth's surface. They have the highest energy and cause the most damage.

    They penetrate just beyond the epidermis (the superficial layer of the skin) and are blocked by glass windows.

    They cause sunburn and contribute to the long-term effects of sun damage (signs of aging and skin cancer).

  • UVA rays have lower energy than UVB rays but penetrate the skin more deeply. They can also travel through glass windows.

    They are responsible for causing sun allergies and can also lead to accelerated skin aging and skin cancer over the long term.

  • Visible light is picked up by receptors in our eyes and allows us to see. It contains all the colors of the rainbow. These range from 390 nm (violet) to 780 nm (red).

  • Infrared rays (780 nm to 1mm) trigger the feeling of heat.

  • Microwaves and radio waves have a longer wavelength (over 1 mm).

The intensity of UV radiation depends on various factors:

The latitude

Solar radiation becomes more intense the closer you are to the equator, where there are more UV rays. The sun's rays in the tropics are vertical which means sunlight is at its strongest.

Altitude

The higher the altitude, the thinner the atmosphere becomes. This means it filters out less UV radiation. There is a 4% rise in UVB intensity every 100m over 300m above sea level.

Cloud cover

UV rays are reflected , absorbed and diffused by the clouds. The higher the cloud density, the lower the UV radiation (a 15% to 75% reduction).

Reverberation

The amount of solar radiation reflected depends on the surface, which makes it more dangerous. UV rays are reflected by water (5%-20% of UV rays are reflected), sand (15%), grass (3%) and especially snow and ice (70%-90%).

The position of the sun

UV radiation becomes more intense the higher the sun is in the sky. This changes depending on the time of day. UV intensity reaches its peak between 11 am and 3 pm.

Benefits

Calorific action

Feeling of heat.

Anti-rickets action

UVB rays encourage the synthesis of vitamin D which is essential for calcifying bones. Exposing areas of bare skin for 10-15 minutes 2-3 times a week is enough to maintain vitamin D levels.

Melanogenesis (tanning)

Melanogenesis is the process of producing melanin. It is the skin's main natural defense mechanism against UV rays. Tanning lasts two days after sun exposure and reaches its peak after 3 weeks of exposure.

Risks

Actinic erythema (sunburn)

Actinic erythema, or sunburn, damages and even destroys cells in the epidermis.

80% of sunburn is caused by UVB, with only 20% due to UVA.

The redness caused by UVB (erythema) is generally biphasic. It provokes an immediate transitory reaction, which begins after a few seconds and lasts no longer than a few minutes. The second phase begins after 3-5 hours, and reaches its peak between 12 and 24 hours after. This lasts around 72 hours.

Benign summer light eruption

This appears the first time skin is exposed to the sun. It predominantly affects women aged 15-35. It causes an eruption of small red spots that are slightly raised like tiny blisters. It has a similar appearance to urticaria and is accompanied by intense itching. These spots are found on the neckline, shoulders, arms, backs of the hands and feet.

The sun's aging effect

Skin exposed to the sun often shows early signs of aging. The sun causes the appearance of wrinkles and brown spots.

The stratum corneum in the epidermis becomes thicker and pigment spots start to appear. UVB rays cause small unsightly brown spots, especially in those with fair skin. These are know as actinic lentigines, solar lentigines, senile lentigines or age spots.

UV rays (and UVA in particular) trigger a release of free radicals in the dermis, which contributes to the destruction of collagen and elastic fibers. This leads to the appearance of deep wrinkles in aged skin. The debris from damaged fibers collects in the skin, creating small fatty deposits and a yellowish skin tone.

Photocarcinogenesis

This term describes the series of events that leads to the formation of sun-induced skin cancers.

Photosensitivity

Certain factors (fragrances, medication, hormonal treatments etc.) increase the skin's sensitivity to the sun.

This means skin reacts when it is exposed to the sun.

Solar urticaria

This is triggered within in a few minutes of sun exposure and automatically disappears in the shade within a few hours. It causes urticarial wheals to appear on the skin, which look similar to nettle rash.

Melasma

This mainly affects pregnant women and is known as the mask of pregnancy. It causes the appearance of irregularly shaped spots on the face, neck and neckline.

Skin cancer

Skin cancer is by far the most common type of cancer in human beings. The number of cases is thought to be rising by 5%-10% in Europe every year. According to the WHO (World Health Organization), 130,000 melanomas and 2 million cases of other types of skin cancer are recorded every year in the world.

1/3 of cancers diagnosed worldwide are skin cancers.

It is believed that melanomas and other skin cancers lead to 66,000 deaths worldwide every year.

There are three different types of skin cancer.

Basal cell carcinoma

This is the most common form of skin cancer (75% of skin cancers) and the least aggressive. There are no precursor lesions. Basal cell carcinoma develops locally only and occurs primarily on exposed areas of the skin (face, neck, hands etc.). Early diagnosis and adequate treatment increases the chances of recovery. 95% of patients presenting with a basal cell carcinoma are diagnosed over 40.

Spinocellular carcinoma

This also develops in the epidermis. It affects the elderly and mostly develops on precursor lesions, primarily in the form of actinic keratoses. This is a locally aggressive carcinoma with metastatic potential and must be treated as soon as possible. With early diagnosis and adequate treatment, the recovery rate is high. Around 15% of skin cancers are spinocellular carcinomas.

Malignant melanoma

This is the most dangerous. It is a malignant tumor in the pigment cells (melanocytes) that can occur in healthy skin or as a result of the deterioration of an already-existing nevus (mole). It can be treated if it is spotted early. Late diagnosis can mean a more aggressive treatment is required to stop cancer cells growing in other parts of the body. It develops in pigment cells in the epidermis and can spread rapidly to other organs. Early diagnosis and treatment increase the chances of recovery. 10% of skin cancers are malignant melanomas.

How do you check your skin?

Checking your skin regularly is essential for spotting malignant melanomas early. You can carry out a self-examination using a mirror, or ask someone to help you.

However, regular check-ups with a dermatologist are also recommended.

  1. Your body, arms raised, front, back and sides in a mirror

  2. The forearms, the tops of the arms and underarms, the palms of the hands.

  3. The backs of your legs, the spaces between the toes, the soles of your feet, the genital areas.

  4. The back of the neck and scalp, working in sections parting the hair, using a hand mirror.

  5. The lower back and buttocks.

  6. If you have the slightest doubt, consult your doctor.

Sun safety rules

Apply the correct amount of product

Safety in the sun

To benefit from the level of protection advertised, make sure you use the correct amount of sun protection and follow these rules:

Avoid sun exposure between 11 pm and 3 pm.

Do not expose babies or young children to direct sunlight.

Use clothing to protect your skin (hat, sunglasses, t-shirt etc.).

Re-apply your sun care product regularly to stay protected, especially after perspiring, swimming or towel-drying skin.

Apply sun protection before exposing your skin to the sun. Using sun protection does not make it safe to stay out in the sun longer.

Over-exposure to the sun poses a serious threat to your health. Check moles regularly using the ABCDE rule.

Moles... a potential danger

Moles are often benign and will not become malignant.

However, any change requires attention as it can be a precursor to the development of skin cancer.

Use the ABCDE rule to check moles regularly.
If you notice any of the following characteristics:

  • Asymmetry
  • Border is irregular…
  • Color is uneven…
  • Diameter is bigger than 6 mm…
  • Evolution

Talk to a dermatologist. Early diagnosis is essential for recovery.

Normal appearance of a mole:

  • Symmetrical and round shape

  • Regular edges

  • Even color (light or dark brown)

  • Diameter of less than 6 mm

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