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Sun Induced Pigmentation

The sun causes an uneven increase in pigment production, which produces irregular colouring (pigmentation) of the skin.

Sun Induced Pigmentation

What is pigmentation?


Pigmentation is skin that becomes darker than the rest. This occurs when areas of the skin produce more melanin, the pigment that gives skin colour.


Melanin


Melanin is the primary pigment in the skin layers. It is usually found beneath the surface of the skin.


The sun and melanin


Skin naturally becomes pigmented due to sun rays or other light exposure. This is a normal protective mechanism. 


Melanin can be thought of as a natural sunscreen for the skin. And that is the reason why you tan.


The colour of pigmentation


The colour of pigmentation depends on how:


  1. How deep the melanin is

  2. The predominant type of melanin



Depth of melanin


Melanin at the surface of the skin is brown. Deeper melanin is blue-grey and appears black.


Type of melanin


There are two types of melanin; eumelanin and pheomelanin. There is usually 75% eumelanin in the skin compared to 25% pheomelanin.


Eumelanin is brown or black, whilst pheomelanin is reddish yellow. Eumelanin is the primary determinant of skin colour.

The more you have, the darker your skin. Eumelanin protects the skin from sun exposure, whilst pheomelanin can produce harmful free radicals. 


Melanin and Sun Exposure 


The amount of melanin in the skin increases with UV exposure. The more melanin you have, the deeper the tan. This is something we, unfortunately, associate with looking healthy.


What is in daylight?


The light that we see during the day is made up of different types or wavelengths.


Types of light include:


  • Visible light 40%

  • Ultraviolet radiation 10%

  • Infrared 50%


40% of light is made up of visible light (what you see). The rest, most of which is harmful, you can't.


UVA versus UVB


The skin colour change with UVA differs from UVB. This is because UVA penetrates the skin deeper than UVB.


UVA gives a greyish tone, whilst UVB is browner.


UVA


UVA exposure results in immediate skin darkening. Tanning from UVA does not provide you with long-term protection from the sun. And is the main reason your skin ages, thickens and develops wrinkles (A = Ageing).


Unlike UVB, you are exposed to UVA “all day long”, and it passes through clouds, rain, wind, and car windscreens


UVB


UVB exposure causes immediate redness and a tan 2-3 days later as the amount of melanin increases.


Although UVB only makes up 0.5% of the light reaching the earth (20 x less than UVA), it is enough to cause Burning when you are exposed to the sun (B = Burning).


UVB facts


UVB damages the outermost layers of your skin. UVB is the cause of suntan, sunburn and blistering. The amount of UVB changes during the day, peaking between 10 am and 4 pm. UVB rays do not penetrate glass.


Signs of sun damage to the skin


Signs of sun damage, with the main UVR, highlighted in (brackets), include:


  • Reduced collagen levels (UVB)

  • Areas of thick skin (UVB)

  • Areas of thin skin (UVA)

  • Wrinkles (UVA) 

  • Dark pigment spots on the skin (called liver or sun spots - UVA)

  • Solar elastosis (yellow, thickened skin - UVB)


Skin cancer and tanning


Everyone knows the importance of wearing sunscreens to prevent skin cancer.


Despite advice to use skin protection, skin cancer is rising at an alarming rate.


There are three primary skin cancers thought to be linked to sun exposure:


  • Basal cell carcinoma (BCC)

  • Squamous cell carcinoma (SCC)

  • Melanoma.


You are more likely to develop BCC and SCC if you:


  • Live in a sunny area.

  • Spend a lot of time in the sun.

  • Have signs of photo-ageing.


Melanoma is linked to intermittent rather than constant sun exposure (like taking vacation holidays).


A history of previous sunburn puts you at risk of all three.


Sunscreens


The first sunscreens only blocked UVB. However, UVA is one of the main risk factors for melanoma development. Sunscreens should therefore block both UVA and UVB.


Applying sunscreen


It is well known that we don’t use enough sunscreen. Enough means applying sunscreen to a proper thickness and spreading it evenly. 35ml is the minimum amount of sunscreen to cover the whole body.



The reality is that most users only give themselves 20-50% protection. That is, we only apply 7ml to 17.5ml. This means an SPF of 15 is only 5!



All sunscreens lose their effectiveness with time when exposed to the sun's rays. This is why we must keep applying every 2-3 hours throughout the day.


Types of Sunscreen


There are two types of sunscreen - physical and chemical.


Chemical


Chemical sunscreens absorb UV radiation but release free radicals and may cause allergies. Physical sunscreens reflect UV rays, but not all of them.


Chemical sunscreens take up to 20 minutes to provide complete protection. They also heat up when in the sun due to a chemical reaction.


Chemical sunscreens are easier to apply, colourless and more user-friendly. They are commonly combined with physical sunscreen. Sensitive skins may react to some of the chemicals used - most people wrongly think this is an allergy which, fortunately, is very rare.


Physical


Physical sunscreens block the broadest range of light, are not absorbed and rarely cause allergic reactions, so they are better tolerated by most skin types. They also work straight away.


Unfortunately, physical sunscreens have a white appearance on the skin, are thicker and more challenging to apply. Physical sunscreens reflect rather than absorb UV radiation. The best-known physical sunscreens contain Zinc or Titanium oxide.


When should you apply sunscreen?


Sunscreen should always be applied 30 minutes before sun exposure, especially on the beach. Sunscreen should also be applied directly onto the skin before any makeup.



What should you do in addition to applying sunscreen?


Even though wearing a daily broad-spectrum sunscreen is essential, we know this is not enough.


Other “skin-protecting behaviours” should include:


  • Staying in the shade.

  • Wearing SPF-rated clothing.

  • Wearing hats (provides an SPF of 5).

  • Wearing UV-blocking sunglasses.

  • Sun avoidance - not going in the sun between 10 am and 4 pm.


Sunbeds


A tan achieved from a sunbed (which uses UVA) does not provide the same protection as a tan from UVB.


This gives a false sense of security to people who go brown and is one reason tanning beds are so harmful.

References

Baumann's Cosmetic Dermatology, Third Edition by Leslie S. Baumann, Evan A. Rieder, et al.

https://amzn.eu/bvrZ2Cz

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