The myth of the healthy tan: what are the effects of sun exposure on the skin?

Yellow parasol with blue sky


A positive effect of the sun on the psyche is generally known. Sunbathing boosts vitamin D production. The "sun vitamin" influences the formation of serotonin and dopamine, which in turn can lift your mood and improve your mood. You get a tan, which is perceived as attractive and healthy. But how healthy is tanning actually and what effects does it have on the body when the skin tans?

Yellow parasol with blue sky

Die Sonne sendet UV-Strahlen aus (grafxart8888 / iStock)

What happens during sunbathing?

The sun emits UV rays, which hit the human organism during sunbathing. While the short-wave UVC rays are shielded by the ozone layer, up to 10% of the longer-wave UVB rays reach the earth's surface unfiltered and the UVA rays almost completely. Depending on the wavelength, UV radiation also penetrates the skin to different depths.

UVA rays penetrate as far as the dermis. There they cause pigmentation of the skin within a few minutes by darkening existing melanin. The mobilization of the color pigment into the outer layers of the skin is an immediate protective mechanism of the body against UV radiation. Due to the rapid tanning effect, the UVA value in solariums is higher.

The higher-energy UVB rays penetrate less deeply into the skin and cause the melanocytes located in the epidermis (outer layer of the skin) to produce melanin. The body's own color pigment is distributed in the upper skin cells and becomes apparent after a few days in the tanning of the skin. In this way, the organism tries to build up a natural self-protection. The more melanin is deposited in the skin cells, the darker the tan of the skin appears.
UVB rays also have an essential function for the body: they support the metabolism in the formation of the body's own vitamin D, which accounts for about 80 % of the requirement.

Melanin protects the skin from UV radiation, but only to a limited extent

The formation of melanin in the melanocytes is stimulated as soon as UV rays hit the skin. Melanin converts light energy into heat energy and thus protects the genetic material of the cells from damage or destruction by UV radiation. However, the protective effect is limited in time and varies according to skin type. As a rule, the protection lasts only for a few minutes to a few hours. The amount of melanin produced and consequently the duration of self-protection depends on various factors. In addition to the strength of the UV light, such as in summer, the tanning intensity is primarily genetically determined. The darker the skin and hair color, the more melanin is produced by the body. Age, hormonal changes and medication can also influence melanin production.

Risks and damages of excessive sun exposure

UV rays emitted from the sun are classified as carcinogenic and cause short- and long-term damage to the skin and eyes.

Acute effects:

The skin can withstand short-term sun exposure without initially developing visible damage. The limit of UV dose up to which no acute consequences occur after natural or artificial UV radiation is called the "erythema threshold".
As early as 5 to 10 minutes after intense sun exposure, the erythema threshold is exceeded in people with a fair skin type, resulting in UV damage in the form of a sunburn. The red coloration of the skin, which resembles a burn, is caused by the UVB rays and is an inflammatory reaction of the skin.
Depending on the degree of the burn, the skin may hurt, itch, blister, peel or even scar. Intense sun exposure can also cause circulatory collapse or fever.

Apart from this burn damage, even a small amount of UVB radiation is sufficient to alter the DNA, i.e. the genetic material of the skin cells. Although this can be compensated by the body's own repair system of the cells, frequent and intensive UV exposure and recurrent sunburns can cause irreparable damage. Permanent changes (mutations) occur, which can promote the development of skin cancer in the course of a lifetime.

Even tanned skin offers no protection against genetic damage. Although it takes longer for sunburn to occur in tanned skin compared to non-tanned skin, tanning in no way means that the skin is protected from genetic damage caused by UV radiation. Thus, the risk of developing skin cancer remains even with tanned skin.

Excessive sun exposure can also damage the eyes and cause painful symptoms such as conjunctivitis or corneal inflammation.

Late effects:

With prolonged UV exposure, the skin's cell division increases, causing the skin's top protective layer to thicken and form a so-called light callus. Although this UV self-protection delays the occurrence of a noticeable sunburn, it also does not prevent long-term cell damage. The general adaptability of the skin to intensive sun exposure depends on the skin type. For example, the skin of people with very light skin, light eyes, reddish-blond hair and frequent freckles is hardly able to tan or form a light callus.

Close up of eye with wrinkles UV-Strahlen beschleunigen die Hautalterung (dolgachov / iStock)

A well-documented long-term effect of UV radiation is premature skin aging. UVA rays produce free radicals, which can damage collagens in the connective tissue and prevent their regeneration. As a result, the skin loses elasticity and forms wrinkles. Solarium use accelerates this aging process of the skin, since in solariums the UVA value of the light is usually higher due to the faster tanning. Frequent sun exposure also promotes the formation of birthmarks and freckles and can cause so-called "age spots".

Intense and prolonged UV radiation can lead to lens clouding of the eye, better known as cataracts. UVA radiation penetrates to the retina of the eye and causes retinal changes such as macular degeneration, which can cause impaired vision.

Excessive UV radiation weakens the immune system and thus the body's defenses against infections or cancer cells.

Skin cancer

UV radiation is considered the main cause of skin cancer. Exposure to radiation adds up over a lifetime. The majority of skin cancers are first detected between the ages of 75 and 79. Sunburns experienced in childhood and adolescence increase the risk of developing skin cancer two- to threefold in later life. In Germany, approximately 224,000 new cases of skin cancer are recorded each year (as of 2015). The incidence also doubles every ten to fifteen years.

Biopsy of basal cell carcinoma Histologisches Bild eines Basalzellkarzinoms (Md Babul Hosen / iStock)

Different UV rays promote different types of skin cancer. UVB rays mainly cause basal cell carcinomas and squamous cell carcinomas. UVA rays, on the other hand, play a major role in the pathogenesis of melanomas (black skin cancer). Melanomas are the most malignant forms of skin cancer, affecting about 1,500 people per year in Austria (as of 2019). In addition, almost 90% of all deaths due to skin cancer are due to malignant melanoma.

In addition to the number of sunburns, skin type, the number of moles and individual UV exposure also influence the risk of skin cancer. Tanned skin and dark skin types are also at risk for skin cancer.

Sun protection and UV index

Protection from UV radiation is the most important measure to reduce the risk of skin cancer. An important guide is the UV index . This measures the strength of the sunburn-effective UV radiation near the ground. The higher the UV index, the more intense the UV radiation and the faster damage to the health of unprotected skin occurs. From a UV index of 3, the skin should be protected from the sun's rays, and from a UV index of 8, we speak of very high radiation exposure, at which point effective protection is urgently required and the sun should be avoided at all costs.

UV scale Der UV-Index wird auf einer Skala von 1 bis 11+ angegeben (gentle studio / iStock)

The Federal Office for Radiation Protection recommends protecting oneself from sunlight from a UV index of 3. Direct sunlight on the skin, especially during midday, should be avoided and shade sought instead. Areas of the body exposed to the sun should be covered with clothing and headgear. Wearing sunglasses with UV-protective lenses can protect the eyes. On naked parts of the body, it is recommended to apply a sunscreen with sufficiently high UVA and UVB filters. By the way, this only works if it is applied correctly and in the right amount: To obtain full protection, 2 milligrams per square centimeter of skin must be applied, which is roughly equivalent to 4 heaping tablespoons of sunscreen for the whole body in adults. To maintain the effectiveness of the sunscreen, the skin must be reapplied at regular intervals. The sun protection factor (SPF) of a sunscreen extends the self-protection of the skin by the factor indicated, i.e. an SPF of 30 extends a self-protection of 10 minutes to 300 minutes. The self-protection time differs according to skin type and is 5-10 minutes for very fair-skinned people and up to 60 minutes for a very dark skin type.

Little girl sitting on beach under umbrella Kinder und Babys müssen besonders gut vor der Sonne geschützt werden (goce / iStock)

Children's skin is more sensitive than adults', which also makes it particularly susceptible to sunburn. Sun damage in childhood influences the risk of disease in adulthood. Young children in particular should be especially protected from the sun's rays and wear sun-proof clothing and headgear. In addition, children should be covered with a suitable sunscreen with an SPF of at least 30. The higher the SPF, the better.

Vitamin D is formed despite sun protection

The main source for the body's own production of vitamin D is UVB rays. When the skin comes into contact with sunlight, the body's own provitamin D is converted into the active form of vitamin D3. The fat-soluble vitamin is involved in bone metabolism and influences muscle strength. It is involved in the formation of hormones and neurotransmitters such as serotonin and dopamine and has possible, but not sufficiently proven, positive effects on the psyche and the immune system. The body's own synthesis depends, among other things, on the season, weather and geographical location. According to current knowledge, it is sufficient to expose the hands, face and partially the arms or legs to the sun for a few minutes, uncovered, 2-3 times a week in order to form sufficient vitamin D. The UV light required for this is equivalent to the amount of vitamin D produced by the body. The UV light required for this corresponds to the minimum sunburn-effective dose: in the summer months this corresponds to 5-10 minutes (for lighter skin types) or 10-15 minutes (for darker skin types) of sun exposure during the midday hours. For months with less sun, vitamin D is partially stored in fat and muscle tissue. Infants, who should generally not be exposed to direct sunlight, are usually given vitamin D during the first year and a half of life to prevent rickets (bone disease in children and adolescents).

Solarium - a better alternative?

Any form of UV radiation is harmful to the human organism - including the UVA rays used in solariums. The risk of developing black skin cancer is significantly higher in people who regularly visit tanning salons. Contrary to assumptions that a visit to the tanning salon also boosts vitamin D production, UVA radiation does not contribute to vitamin synthesis, but may even promote its breakdown. Despite the tan obtained, visits to the solarium do not reduce sunburn sensitivity, as UVB rays are also needed for this. The so-called "pre-tanning" in the solarium only leads to unnecessary exposure to additional, artificially generated UV radiation, which increases the risk of skin cancer.


Sunlight contains UV rays, some of which penetrate deep into the skin and damage the genetic material of skin cells. The rays cause the skin to age faster and promote the development of skin cancer. Sunburns are externally acute consequences of excessive UV exposure and increase the risk of developing skin cancer. The tanning induced by the color pigment melanin is, contrary to many contrary assumptions, a sign of skin damage, as it is an attempt by the body to protect itself from further damage caused by UV radiation. Also, the tan produced in the solarium is by no means beneficial to health, but continues to increase the risk of developing skin cancer. Sufficient sun protection and avoidance of direct UV radiation is therefore essential in the case of medium to strong UV radiation. Since it is practically impossible to completely protect the body from sun exposure and the body only needs a few minutes of sun exposure to form enough vitamin D, there is usually no need to fear a vitamin D deficiency during the summer months.


Editorial principles

All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.
Olivia Malvani, BSc

Olivia Malvani, BSc

As a student of nutritional sciences, she writes magazine articles on current medical and pharmaceutical topics, combining them with her personal interest in preventive nutrition and health promotion.

Dr. med. univ. Bernhard Peuker, MSc

Dr. med. univ. Bernhard Peuker, MSc

Bernhard Peuker is a lecturer and medical advisor at Medikamio and works as a physician in Vienna. In his work, he incorporates his clinical knowledge, practical experience and scientific passion.

The content of this page is an automated and high-quality translation from DeepL. You can find the original content in German here.

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