Many people associate a tan with health, beauty and an active lifestyle. Although a moderate dose of solar radiation is indispensable for our health, unfortunately, there is no such thing as a real "healthy tan" or "healthy sun-kissed glow" as it is always a visible sign of skin damage. Tanning is a response by the skin to exposure to ultraviolet (UV) radiation (and HEV or Blue Light), either from natural sunlight or artificial sources like tanning beds which leads to photo-ageing, pigmentary disorders (like age spots or hyperpigmentation) and immunosuppression, hence skin cancer. When skin is exposed to sunlight: UV rays and high energy visible light (HEV) or also called Blue Light (the most energetic region of HEV), it produces more melanin, a pigment that darkens the skin as a (partial) protective mechanism to prevent further damage. The amount of artificial blue light emitted during the conventional use of electronic devices is not enough to trigger harmful skin effects. (Click here to read more)
MELANIN Melanin is only produced by cells called melanocytes, mostly distributed in the epidermal-dermal junction. Melanocytes contain specialized organelles called melanosomes to store and produce melanin. Melanosomes are transferred from the melanocytes to the neighboring keratinocytes, which are the most abundant cells in the epidermis. One melanin-forming melanocyte surrounded by 36 keratinocytes and a Langerhans cell is called the melano-epidermal unit. [1.2] Melanocytes use the amino acid tyrosine to produce melanin and protect epidermal keratinocytes and dermal fibroblasts from the damaging effects of solar radiation.. [13] The are two melanin pigment classes:
Differences in skin pigmentation do not result from differences in the number of melanocytes in the skin, as one might assume, but from differences in the melanogenic activity (melano-competence), the type of melanin produced in melanosomes (the ratio between eumelanin and pheomelanin differs per Fitzpatrick phototype) and the size, number and packaging of melanosomes, with melanin content of melanosomes ranging from 17.9% to 72.3%. [7] The amount of melanin is never enough for adequate photoprotection, and a "base tan" does not prevent sunburn. Particularly darker phototypes are more sensitive for the damaging effects of Blue Light. Both eumelanin and pheomelanin production are promoted by UV radiation and Blue Light and therefore sunscreens offering a combination of both UV (A + B) protection and Blue Light defense are recommended for all phototypes. TANNING PROCESS The skin's tanning process occurs in four distinct phases: [3]
ROLE OF UVA, UVB AND BLUE LIGHT One of the most important acute effects of UVR is DNA photodamage. UVA and UVB show different properties regarding their biological effects on the skin. [7] Shorter wavelengths (nm) correspond to higher energy. Infrared does not induce oxidative stress. Read more UVA radiation (320-400 nm) penetrates deeper into the skin and can induce indirect DNA damage by the generation of reactive oxygen species (ROS), leading to premature skin aging. UVA, in contrast to UVB is not filtered by window glass, is able to penetrate deeper into the skin and reach the dermis. They are present constantly, with relatively equal intensity, during all daylight hours throughout the year. It has been estimated that 50% of exposure to UVA occurs in the shade. UVA rays are less intense than UVB, but there are 30 to 50 times more of them. To produce the same erythemal response, approximately 1000 times more UVA dose is needed compared with UVB. [7] The bulbs used in tanning beds emit mostly UVA. UVB radiation (280-320 nm) is less prevalent than UVA, primarily affects the outermost layers of the skin, causing direct DNA damage (more potent than UVA) and triggers inflammatory responses that lead to increased melanin production. UVB radiation fluctuates throughout the day, are at their strongest at noon. and are more cytotoxic and mutagenic than UVA. The action spectrum for UV-induced tanning and erythema are almost identical, but UVA is more efficient in inducing tanning whereas UVB is more efficient in inducing erythema (redness). Dark skin is twice as effective compared to light skin in inhibiting UVB radiation penetration. [7] UVB helps the skin to produce Vitamin D. Blue light (400-500 nm) visible light accounts for 50% of sunlight [11] and can contribute to immediate, delayed, continuous and long-lasting pigmentation by activating melanocyte-specific photoreceptors and increasing melanin synthesis, particularly in individuals with darker (melano-competent) skin types [9], cause DNA damage [10] and generate damaging reactive oxygen species in both the epidermis and the dermis. [12] The effects may last longer than those induced by UVA and UVB radiation. Blue Light can penetrate even deeper than UVA and reach the hypodermis. Blue light therapy is used to target acne causing bacteria and inflammation, however the risks might outweigh the benefits especially in darker phototypes and it might worsen acne marks. EPIDERMIS AND DERMIS Both dermal fibroblasts and epidermal keratinocytes play a crucial role in regulating skin pigmentation and tanning response. [13 15] In comparison to epidermal tanning, dermal tanning is less visible, however more immediate. Dermal fibroblasts secrete various paracrine factors that regulate melanocyte function, survival, and melanin production. Factors like hepatocyte growth factor (HGF), nerve growth factor (NGF), stem cell factor (SCF), and basic fibroblast growth factor (bFGF) stimulate melanogenesis and pigmentation [14 15] Fibroblast senescence and altered secretory profiles in conditions like melasma contribute to abnormal pigmentation by stimulating melanogenesis. [15] Epidermal keratinocytes produce factors like α-melanocyte stimulating hormone (α-MSH) and Wnt1 that activate melanogenic pathways in melanocytes, leading to increased melanin synthesis and transfer to keratinocytes. [15 16]. Keratinocyte-derived exosomes can enhance melanin production by melanocytes. [16] Differences in autophagic activity between various keratinocytes also influences pigmentation. [15] MicroRNAs MicroRNAs are small, non-coding RNA molecules that regulate gene expression by binding to messenger RNA (mRNA) and typically suppressing protein production, for example collagen. They are classified as epigenetic modulators. Several miRNAs have been identified as differentially expressed in aged skin compared to young skin, including: - miR-383, miR-145, miR-34a (upregulated in sun-exposed aged skin) - miR-6879, miR-3648, miR-663b (downregulated in sun-exposed aged skin) [17] Enjoy the sun, however protect your (and your children's) skin from a photo-damaging tan to remain skin health and beauty. Sunless self-tanning products containing dihydroxyacetone (DHA) or Erythrulose provide a safe alternative to achieve a "sun-kissed" glow. You can use after-sun skin care which helps to rehydrate, reduce damage of "sun-stressed" skin and support it's repair. Always consult a qualified healthcare professional or dermatologist to determine what the most suitable approach is for your particular skin condition and rejuvenation goals. Take care! Anne-Marie References
Comments
|
CategoriesAll Acne Ageing Aquatic Wrinkles Armpits Biostimulators Blue Light & HEVIS Cleansing CoQ10 Cosmetic Intolerance Syndrome Deodorant Dermaplaning Diabetes Dry Skin Epigenetics Evidence Based Skin Care Exfoliation Exosomes Eyes Face Or Feet? Facial Oils Fibroblast Fingertip Units Gendered Ageism Glycation Gua Sha Hair Hair Removal Healthy Skin Heat Shock Proteins Hormesis Humidity Hyaluron Hyaluronidase Hypo-allergenic Indulging Jade Roller Licochalcone A Luxury Skin Care Lymphatic Vessel Ageing Malar Oedema Menopause Mitochondrial Dysfunction Mood Boosting Skin Care Neurocosmetics Ox Inflammageing PH Balance Skin Photo Biomodulation Polynucleotides Psoriasis Regenerative Treatments Review Safety Scarring Sensitive Skin Skin Care Regimen Skin Flooding Skin Hydration Skin Senescence Skip-Care Sleep Slugging Sunscreen Tanning Under Eye Bags Vitamin C Well Ageing Skin Care Wound Healing Wrinkles
Archives
April 2024
|
RSS Feed
