Why Skin Changes Color and How to Prevent Pigmentation

Humans have an amazing ability to change skin tone as a part of adaptation to environmental challenges as well as changes in metabolism or health issues. Several pigments define our skin tone, but the most important of them is melanin, produced by skin pigment cells called melanocytes. 

What Is Melanin?

Melanin is a dark natural pigment produced by the pigment cells. Melanin pigment is vital for our skin health due to its sun protection factor from ultraviolet radiation and free radicals, constantly adjusting to changing environmental conditions.

The shielding effect of melanin, especially dark eumelanin, is achieved by its ability to serve as a physical barrier that scatters ultraviolet radiation. Also, it acts as an absorbent filter that reduces the penetration of ultraviolet through a superficial skin layer.

The efficacy of melanin as a sunscreen was assumed to be about 1.5-2.0 sun protective factors (SPF). Possibly, it can be as high as 4 SFP, implying that melanin absorbs 50% to 75% of harmful radiation. An SPF of 2 means the natural melanin doubles our skin's protection against sunburn.

You can guess that is not enough to protect the skin from damage, but our skin melanin creates a natural barrier that helps protect our skin at some basic point. In the case of a skin condition called albinism, when the natural pigment melanin is absent, there is an increased risk of sun damage. The skin is more vulnerable and needs to be protected carefully, even when the intensity of ultraviolet rays is very low. 

5 Facts About Melanin

  • There are many different types of melanin! Common in the human body are dark brown eumelanin, yellow or red pheomelanin, and neuromelanin located in nervous cells. 
  • Melanin defines not only the skin tone but also the hair and eye color. The more melanin you have, the darker your hair, eyes, and skin will be, but eye or hair color cannot change because of environmental factors, as skin tones do. 
  • Melanin can be found not only in eyes, hair, and skin but also in the brain, inner ear, and adrenal glands. 
  • The main function of melanin is not only a protection against ultraviolet radiation but also an antioxidant protection of skin cells against free radicals. 
  • Melanin can degrade after ultraviolet and sun exposure, releasing histamine. It can cause "sun allergy," manifesting itself through swallowing or puffiness, itchiness, and other symptoms. It happens more often in people with lighter skin tones as lighter pheomelanin is less stable. 

Melanocytes or Pigment Cells

Melanin produced by specific skin cells is called melanocytes. They are located between the superficial skin layer called the epidermis and the deep skin layer called the dermis.

Melanocytes have a very similar structure to nervous cells and are sometimes called "skin neurons" as they are able to interact with the nervous system using the same biochemical language. Melanocytes form about 1% of all epidermal cells, but each pigment cell is associated with about 36 of the main epidermal cells called keratinocytes and one immune Langerhans cell, forming a small molecular structure known as the epidermal melanin unit.

Each melanocyte plays the role of a sun umbrella for 30-40 keratinocytes (main epidermis cells), protecting them from damage and mutations. MEach pigment cell has a special structure called melanosome which produces melanin. Melanin doesn't stay inside pigment cells for long, as pigment cells are able to transfer protective pigment to other cells using dendrites. Dendrites look like octopus tentacles growing from melanocytes, adjusting to other cells in the skin and transferring melanin to them, helping to protect their DNA from within. 

How Is Melanin Synthesized by the Skin? 

While skin is exposed to ultraviolet radiation, it triggers special receptors of pigment cells, which activate a reaction of melanin synthesis. The main source of melanin is the amino acid tyrosine, which circulates in our body. Tyrosine is oxidized and transformed into a new substance called DOPA, which can be transformed into dark brown eumelanin or yellow/red pheomelanin if reacting with sulfur-based amino acid cysteine.

Ultraviolet radiation triggers mostly brown melanin production, changing skin color to darker. A key substance transforming tyrosine to melanin is called tyrosinase. It is an enzyme produced by pigment cells while they are exposed to hormonal influence, inflammation, trauma, or stress, as well as ultraviolet.

Simply speaking, more tyrosinase means darker skin color in the area exposed to sun rays. Skin damage or sensitization by different agents provoques higher sensitivity of pigment cells' receptors and higher activity of tyrosinase, leading to excessive melanin production and formation of dark spots or discoloration. 

Sun Sensitivity: Post-Inflammatory Hyperpigmentation

Skin light sensitivity (photosensitivity) means you have an unusual reaction to sun exposure. This can cause symptoms like pain, redness, skin inflammation, itching, or a rash when the skin is exposed to light, followed by pigmentation issues like the formation of dark spots and melasma. You can become photosensitive from:

  • Medications: Some widely used medications, including antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or paracetamol, anti-allergic medications, antidepressants, contraceptives and certain heart medicines and statins for lowering cholesterol, can make your skin far more sensitive to sunlight than you'd usually be. Sun-sensitizing drugs can also aggravate an existing skin condition such as skin sensitivity, acne or rosacea. 
  • Diseases and medical conditions: Certain medical conditions and disorders, including endocrine conditions, autoimmune diseases like lupus, and others, can make people hypersensitive to UV rays. A higher risk of photosensitivity is found in people with rosacea, atopic dermatitis, eczema, and psoriasis. 
  • Skincare: Certain ingredients in skincare, such as retinol, glycolic acid, kojic acid, salicylic acid, azelaic acid, or benzoyl peroxide, remove the outermost layer of skin to fight fine lines or acne scars. Skin-lightening creams that contain whitening agents may decrease the amount of melanin in your skin, which acts as a natural defense against the sun's rays. These may cause photosensitivity and increase your chances of damage from UV exposure. 
  • Photosensitizing ingredients are found in makeup and perfumes, such as fragrances and essential oils. Paradoxically, some of the chemicals used as sunscreen filters can cause photosensitive reactions and contact dermatitis as well.

If you have a family history of skin photosensitivity or it was increased by some sensitizing agents, it is important to be very careful and use broad spectrum sunscreen avoiding sun exposure during mid-day when the intensity of ultraviolet rays is higher. 

Is there a Genetic Difference? 

Individuals with a darker skin tone are better protected against sun-induced damage, as their skin contains more of protective eumelanin which is superior to pheomelanin in its photoprotective properties. Interestingly, the melanin in darker skin tones is twice as effective compared to lighter skin in inhibiting UVB radiation from penetrating into the skin.

Scientists found that the darker skin allows only 7.4% of UVB and 17.5% of UVA to penetrate through epidermis, but 24% of UVB and 55% of UVA pass through fair skin structure. Melanosomes in dark skin are more stable and resistant to degradation, while in lightly pigmented skin, melanosomes are easily degraded, distributing a "melanin dust" in the superficial skin’s layers. That explains the higher risk of skin cancers in people with fair skin types and the importance of intense and persistent sun protection. 

Differences in skin pigmentation do not result from differences in the number of pigment cells in the skin, as one might assume, but from differences in their activity, the type of melanin produced, and the size of melanosomes. The amount of pigment in one pigment cell can vary, with the melanin content of melanosomes ranging from 18% to 72%, defining a darkness of skin color.

Melanocyte density in the skin of the palms and soles is only about 10-20% of that in the skin on the trunk or limbs, so their color is always lighter. Red hair can contain high levels of pheomelanin, but generally, all types of skin contain more of dark eumelanin than red/yellow pheomelanin.

While total melanin content in the epidermis differs only by 2-fold in Asian and Caucasian skin, Black skin contains ∼3 to 6-fold higher levels of melanin, more eumelanin and has more and larger melanosomes than fair skin.

However, it doesn't mean that people with darker skin types don't need to protect their skin from ultraviolet light! The World Health Organisation recommends using sunscreens and seeking shade when an ultraviolet index is 3 or higher. But even for very sensitive, fair-skinned people, the risk of short-term and long-term UV damage below a UVI of 2 is limited, and under normal circumstances, no special protective measures are needed. 

What Triggers Melanin Production and Post-Inflammatory Hyperpigmentation

  • Ultraviolet is the main trigger of pigment synthesis as melanin plays a key role in skin protection against sun-induced damage. 
  • Inflammation immediately activates melanin production in the affected area via inflammatory mediators produced by skin cells. Dark spots are very common in acne patients but can appear after insect bites or skin trauma, including aesthetic procedures such as microneedling, dermaplaning, mesotherapy, aesthetic injections, laser resurfacing, etc. The use of skin care products provoking skin irritation and redness can cause an inflammatory hyperpigmentation as well.
  • Most important environmental factors causing hyperpigmentation are air pollution and smoking. High concentration of dioxins, as well as other toxins in the air alongside microparticles and VOCs (volatile organic compounds), damages skin and leads to the over-expression of receptors in pigment cells. Chemical skin damage provoques uneven distribution of melanin and the formation of dark spots in exposed skin areas such as the face, neck, decollete, or hands. 
  • Hormonal factors especially increase the risk of post-inflammatory hyperpigmentation, such as pregnancy masks in women or melasma in menopausal women. Multiple hormones are involved in skin pigmentation. Sex steroid hormones, both male and female, can influence pigment synthesis, as well as cortisol and other hormones of adrenal glands. 
  • Sleep has been shown to have an impact on inflammatory processes, hormone levels, and blood flow in skin disorders in general. It is described that psychosocial stress and stress related to sleep deprivation may lead to skin barrier disruption and consequent imbalance of the skin health. This skin injury secondary to stressful effects may decrease cutaneous immune defense and trigger chronic inflammation. Study has shown that the release of alpha melanocortin (α-MSH) plays a role in the development of melasma. Poor sleep quality can increase an expression of the specific cell receptors involved in pigment synthesis as well as hormonal skin receptors, higher expression of inflammatory substrates and growth factors provoking hyperpigmentation. Recovery from sunburn was more sluggish in poor quality sleepers, with erythema (redness) remaining higher over 72 hours, indicating that inflammation is less efficiently resolved and risk of hyperpigmentation following sunburn is much higher. 
  • Stress is one of the lifestyle factors possibly provoking skin dyspigmentation. Stress-related hormones such as cortisol increase the risk of higher skin sensitivity to ultraviolet rays and trigger inflammation in the skin and other organs. Stress is well known as a pro-inflammatory condition worsening severity of acne, rosacea, and many other skin conditions. Stress management  is very important in dermatology or aesthetic therapy, including hyperpigmentation treatment. 
  • Skin aging is characterized by loss of elasticity, formation of wrinkles, an impaired recovery response against damage, increased water loss, and pigmentation. All types of skin cells are involved in skin aging, and the crosstalk between these cells during the aging process may play an important role in the formation of dark spots and melasma. With chronological aging, the number of functional pigment cells gradually declines, and their activity is reduced, resulting in the appearance of pale skin and age spots in elderly people. However, pigment cells of skin regularly exposed to the sun are relatively well-maintained compared with those of unexposed aging skin, most likely due to constant stimulation by ultraviolet rays. Two of the most common pigmentary changes during the aging process are senile lentigo and melasma. Senile lentigo is often observed in the elderly and most commonly occurs on exposed skin areas, such as the face or hands, as brown, dark spots, and patches. Melasma is another pigmentation disorder that develops in sun-exposed skin areas. Although it is not a totally age-related disease, it progresses with age, becoming even more difficult to treat. Cellular senescence gradually progresses with age and affects melanocytes as all other skin cells change their functionality.

The Role of Microbiome in Skin Pigmentation

The latest research found a correlation between characteristics of the skin microbiome and the pigmentation status of the skin. Specific strains of pro-inflammatory bacteria, including C. acnes, have been found to be prevalent in pigmented skin.

In non-pigmented skin prevailed other bacteria strains known for their antioxidant activities. "Antioxidant" bacteria help moderate skin immune reactions, reduce inflammatory reactions, and improve natural protection from ultraviolet. Apparently, the skin microbiome plays an important role in skin protective function but also in skin aging, pigmentation, and the development of skin conditions.

When You Need to Contact a Doctor to Treat Hyperpigmentation

Contact a medical professional for an appointment if you have:

  • Skin discoloration, like dark patches, that causes significant concern;
  • Persistent, unexplained darkening or lightening of the skin;
  • Any skin sore or lesion that changes shape, size, or color as those may be a sign of skin cancer. 

10 Tips To Prevent and Reduce Hyperpigmentation

  • Regularly check Ultraviolet Index (UVI) and protect your skin according to recommendations of the World Health Organization (WHO). 
  • Avoid direct sun exposure during midday and try to stay in shadow when it is possible. 
  • Wear a sun hat, sunglasses, and sun-protecting clothes. 
  • Use sunscreen with an SPF of at least 30, suitable for your skin type. 
  • Use microbiome-friendly skincare rich in antioxidants. 
  • Eat food rich in antioxidants, such as fruits and vegetables. 
  • Take care of sleep hygiene - sleep troubles and circadian rhythm disorders such as jet lag increase skin sensitivity to ultraviolet. 
  • Avoid using photosensitizing skincare products, especially during a sunny season. 
  • Avoid aesthetic procedures such as chemical peels, laser resurfacing, dermabrasion, microneedling, dermaplaning etc during a sunny season. 
  • Avoid photo-sensitizing supplements or medication if possible. 
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