Is tanning safe for your health?

For many people, a golden skin tone is synonymous with holidays and looking well. Yet from a biological perspective, tanning is not a sign of vitality, but a defensive reaction of the body in response to an attack.

The process begins as soon as ultraviolet rays strike the epidermis. These rays cause breaks and mutations in the DNA of skin cells. In response to this damage, melanocytes, specialised cells located at the base of the epidermis, start producing melanin, the pigment responsible for skin colour. This pigment is then distributed to neighbouring cells, the keratinocytes, forming a kind of small protective cap above the cell nucleus, in order to absorb part of the UV rays and protect the genetic material.

Many people believe that once they are tanned, they are fully protected. This is a dangerous misconception. Studies show that tanned skin only provides a natural sun protection factor (SPF) of between 2 and 4. For comparison, a T-shirt made from the thinnest cotton offers a protection factor of 7 to 10. Tanning therefore blocks only a tiny fraction of UV rays and in no way replaces appropriate sun protection.

Exposure to UV radiation is far more than a simple risk of sunburn: it is a silent assault that targets the very structure of our tissues and the integrity of our genetic code.

Classified as definite carcinogens, UV rays act like a sculptor of shadows, altering the memory of our cells long before the first visible signs of their effects appear. We distinguish two types of skin cancer. Melanoma, the most formidable form, often arises from a sudden and intense insult. It is the intense and intermittent exposures, typical of sunny holidays, that trigger the most aggressive mutations. Around 75% of melanomas worldwide result from such excesses. In contrast, carcinomas, whether basal cell or squamous cell, arise from the cumulative effect of every minute of sun received throughout life, preferentially targeting the most exposed areas, such as the face, hands, or scalp.

The development of a cutaneous cancer is based on a specific alteration of the genetic material, initiated mainly by the absorption of UVB energy by the nitrogenous bases of DNA. This phenomenon induces the formation of abnormal chemical bonds, which distort the structure of the double helix. If the repair system does not correct these errors before cell replication, permanent mutations become established. One of the most serious consequences is the inactivation of the p53 gene, a regulatory protein that normally triggers the programmed death of cells that are too severely damaged. Without this protein, the defective cell escapes the natural cycle of destruction and continues to divide, transmitting its genetic instability to the daughter cells, which marks the beginning of the tumoural process.

In parallel with these mutations, UVA rays penetrate more deeply into the dermis and induce a state of chronic oxidative stress through the generation of free radicals. These unstable molecules react with cellular structures, causing indirect breaks in DNA and disrupting the immune environment of the skin. This leads to a functional alteration of Langerhans cells, the sentinels responsible for detecting abnormalities, together with the release of chemical mediators that dampen lymphocyte activity. This local immunosuppression creates a favourable environment in which mutated cells can proliferate without being eliminated by the body’s surveillance mechanisms.

Moreover, contrary to what is commonly assumed, DNA damage does not stop once you leave the sun. Indeed, a recent study has shown that the chemical reactions induced by UV radiation continue to occur in melanocytes for two to three hours after the end of exposure, even if you are in the shade or in complete darkness. The energy stored by melanin is transferred to the DNA with a delay, causing mutations even while you believe you are safe.

Beyond this life-threatening risk, the sun is the main driver of skin ageing, responsible for nearly 90% of wrinkles and pigmentation spots in fair skin phototypes.

Free radicals generated by UVA rays also react with the fibres of collagen and elastin, the proteins of the dermal extracellular matrix responsible for the suppleness and elasticity of the skin. This phenomenon is accompanied by solar elastosis, an accumulation of abnormal elastic tissue that gives the skin a thickened, rigid appearance. At the same time, sunlight weakens blood vessels and disrupts melanin production, leading to the appearance of pigment spots and telangiectasias, which bear witness to past sun exposure.

Beyond the risks of cancer or ageing, the sun can trigger acute inflammatory reactions grouped under the term photodermatoses. The most common of these is polymorphic light eruption, which presents as small red patches and intense itching a few hours after exposure. These conditions result from an inappropriate immune response of the skin to UV radiation. In some cases, this photosensitivity is exacerbated by taking certain medications. Once present in the body, these substances react under UV exposure and cause burns similar to sunburn or allergic-type rashes, even after only short periods in the sun.

This vulnerability of tissues is found, in an even more pronounced way, in the eyes, which lack any pigmentary protection mechanism comparable to tanning. The crystalline lens, by acting as a natural filter to protect the retina, absorbs a massive amount of energetic radiation throughout life. This chronic absorption induces oxidation and denaturation of lens proteins, which aggregate to the point of rendering the lens opaque: this is the mechanism underlying the formation of cortical cataract. On the external surface of the eye, the combined assault of UV radiation, glare and wind can induce the appearance of a pterygium, a proliferative lesion of the conjunctiva that threatens the transparency of the cornea.

Often overlooked, the eye is a direct target of the sun.

Note : The risks associated with tanning are not reduced when using tanning booths; on the contrary, the intensity of UV radiation is increased.

The most thoroughly documented benefit of sun exposure lies in the synthesis of vitamin D, which is essential for bone health and the proper functioning of the immune system. Unlike cancer risks, which increase with cumulative exposure time, the production of vitamin D by UVB rays is a rapid, saturable process.

For most individuals, exposure limited to the face and forearms for just 10 to 15 minutes, two to three times per week, is sufficient to meet the body’s requirements.

Beyond this short period of time, the body stops producing additional vitamin D, and cellular damage begins to accumulate. In parallel with these metabolic aspects, natural light helps to regulate our internal biological clock and our mood. Exposure to daylight, as detected by the retina, stimulates the production of serotonin, the hormone that regulates mood, and helps to prevent downturns in morale.

Moreover, recent studies suggest that spending time outdoors from early childhood may reduce the risk of developing myopia by promoting the release of retinal dopamine, which helps to limit excessive eye growth. Finally, sunlight has a positive effect on the cardiovascular system: UVA rays promote the release of nitric oxide stored in the skin, leading to dilation of blood vessels and a slight decrease in blood pressure.

Here we are talking about moderate exposure to the sun, not long tanning sessions.

To minimise risks and preserve your sun capital while enjoying a pleasant time in the sun, it is important to adopt the right habits (generous and repeated application of sunscreen, wearing protective clothing, avoiding sun exposure between 11 a.m. and 4 p.m. in summer when UV rays are at their strongest, etc.). Another tip for achieving a tanned complexion safely is to use a self-tanner.

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