Effects of the sun on the skin
The exposure of our skin to ultraviolet (UV) radiation from the sun, and the absorption of this ultraviolet energy, causes changes in our body’s chemical, hormonal and neuronal signals, which have subsequent effects on immune cells and vitamin D synthesis, among others (1).
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Benefits of sun exposure
Among the most prominent benefits of exposure to sunlight is the synthesis of vitamin D and all the benefits derived from it. In addition, sun exposure has been scientifically proven to improve sleep and mood.
On the one hand, exposure to sunlight directly modulates the availability of serotonin in the brain, increasing levels of this neurotransmitter, commonly known as the “happiness hormone” (2). Low serotonin levels are associated with an increased risk of seasonal pattern major depression (formerly known as seasonal affective disorder or SAD) (3).
Regarding vitamin D, the primary source of this vitamin is cutaneous synthesis, as it is produced by the body when the skin is directly exposed to the sun (4). The primary function of this vitamin is the absorption of calcium, so its deficiency is directly related to bone diseases (5). It also acts on the cells of the immune system, modulating immune and inflammatory responses. Several epidemiological studies link vitamin D deficiencies to autoimmune diseases, type 2 diabetes, cardiovascular diseases, and, recently, to SARS-Cov-2 infection and death from COVID-19 (6,7).
Risks associated with sun exposure
However, unprotected sun exposure is associated with multiple risks both in the short term (sunburn, sunspots, acne, or photosensitivity) and in the long term (aging and increased risk of skin cancer).
Some of these risks are explained below.
Photosensitivity.
Photosensitivity, sometimes referred to as “sun allergy”, describes sensitivity to ultraviolet light from the sun and other light sources. It can cause skin rashes, fever, fatigue, and joint pain.
It can occur as a result of prescription or over-the-counter medications, a medical condition or genetic disorder, or even the use of certain types of skin care products. There are two different types of photosensitivity reactions: photoallergic and phototoxic (8).
Photoaging.
Skin aging can be divided into two types: chronological or intrinsic aging, which occurs mainly in the photoprotected areas of the body, and extrinsic aging, also known as photoaging. Photoaged skin is characterized by epidermal thickening, dryness, deep wrinkles, loss of elasticity, delayed wound healing, and susceptibility to cancer.
We can say that skin aging is influenced by both intrinsic inherited factors and extrinsic or environmental factors, such as chronic UV exposure and smoking (9,10).
How does photoaging occur? Acute ultraviolet radiation decreases the content of dermal and epidermal hyaluronic acid, the only molecule in the epidermis with the capacity to retain water. Skin aging is associated with moisture loss because of the disappearance of hyaluronic acid from the epidermis (11).
The quantitative balance of risks and benefits is not precisely known, but several studies suggest that it varies according to skin type and genetic make-up (12).
In any case, protective measures should always be taken before exposure to the sun. Some of the most important are the following:
- Wear a hat that shades the face, neck and ears.
- Wear sunglasses that block UV radiation and protect the skin around the eyes.
- Use sunscreen 30 minutes before going outside and reapply every 2 hours or after swimming or sweating.
- Avoid the most intense hours of sunshine.
What role does your genetics play?
The skin is the largest organ of the body and there are almost as many skin types as there are people in the world. The different characteristics that define your skin are given by your genetics and your environment, that is, by your DNA and by all the things that have happened to you throughout your life. Two people with the same skin tone may have different sensitivities to the sun, or different predispositions to photoaging and sunspots and, in many cases, these differences can be seen in the DNA.
Skin can be sensitive to the sun for a variety of reasons, including genetics. Genes related to skin pigmentation and low tanning ease have the greatest influence on our skin’s sensitivity to the sun. Among these genes is the ASIP gene, which encodes the Agouti signaling protein, which is responsible for the distribution of melanin (13,14).
Melanin is a very broad term, used to describe natural pigments found in most living organisms that have numerous functions, including pigmentation (providing color to the skin, hair, and eyes), radical scavenging, radiation protection, and thermal regulation (15).
Another consequence of the sun that is closely related to genetics is sunspots. Facial sunspots (solar lentigines) are oval or round pigmented spots measuring 2 to 20 millimeters, brownish in color, uniform, and located on frequently sun-exposed areas such as the face, arms, or back of the hands. They are larger than freckles/ephelides, do not disappear in winter, and are common in aging skin. Solar lentigines are the result of the local growth of melanin-producing cells in response to UV radiation. These spots are more common in Caucasian and Asian populations and in women, especially after the age of 50. Although they are benign lesions that do not require medical treatment, they indicate excessive exposure to the sun.
Variants in the MC1R gene have been associated with an increased predisposition to sunspots. As previously mentioned, melanin is a very broad term, and there are various forms of melanin. The melanocortin 1 receptor, a protein directly related to the MC1R gene, controls which type of melanin melanocytes produce: eumelanin or phaeomelanin. The relative amounts of these two pigments will determine the color of a person’s hair and skin (16). In addition, several studies point to the contribution of variants in this gene to the appearance of sunspots with age, via a pathway independent of melanin production (17).
Finally, the role of genetics in photoaging should be highlighted. Variations in the FBXO40 gene, among others, have been associated with an overall photoaging score that combines factors such as pigmentation irregularities, wrinkles, and skin sagging. If the FBXO40 gene was not known to function in the skin, how does it affect photoaging? This gene is related to the IGF1 pathway, a hormone that regulates the effects of growth hormone in the body plays an important role in inflammation processes and is also directly linked to myogenesis (the process of muscle tissue formation), which could explain its impact on the severity of wrinkles and sagging (10).
24Genetics and skin care
At 24Genetics we offer you our skin report, in which we analyze how your genetics influence multiple skin characteristics, such as photoaging or antioxidant capacity, which play a key role in the skin’s evolutionary process.
Furthermore, in this report, you will not only find information on how sun exposure affects your skin, but you will also be able to find out your skin’s predisposition to other factors, such as varicose veins or psoriasis, among others.
Bibliography
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