SHEDDING NEW LIGHT ON AN OLD TOPIC.

Are there any good reasons NOT to wear sunscreen? Surely not…

We know well enough of the dangers of skin cancer, which may not only be deadly as the dreaded melanoma, but also disfiguring and requiring numerous visits to the doctor’s office for multiple interventions. In addition, excessive sun exposure causes photo ageing and hyperpigmentation which is distressing to women and men alike.

Sunlight is certainly not all bad, and generally induces a sense of well-being, decreases the appetite, improves libido and assists with the synthesis of vitamin D.  South Africans are a sun loving society that embraces an outdoor lifestyle. While moderate and responsible exposure to the sun is good for your well-being, it is not possible to tan without damaging skin cells, leading to accelerated ageing, and increasing your risk of skin cancer.

As we head into 2021 hoping for a better year than the last, I thought we would relook at some of the controversies surrounding sunscreens and shed some light on new innovations and considerations concerning sunscreen use.

With conflicting information in the media many people are confused about whether they should be wearing sunscreen and uncertain of the product to choose. This can lead to them wearing no sunscreen at all. Let’s set the record straight.

The first point to make clear is that there is overwhelming scientific evidence that excessive sun exposure causes skin cancer and methods of sun protection including sunscreens can prevent this. Recent sunscreen studies conducted in Australia estimate that the current sunscreen recommendations have decreased the incidence of skin cancer by 10-15 %.

Sunscreen and Vitamin D

Possibly the current biggest controversy surrounding sunscreen use relates to Vitamin D deficiency. Reports have been conflicting. A review article published in the British journal of Dermatology last year sought to evaluate the available studies and concluded that there was not enough evidence to suggest that sunscreens decreased the production of Vitamin D. The original study that made this claim was done with an artificial light source different to what people are normally exposed to in the environment. Subsequent studies with real life circumstances could not prove a decrease in Vitamin D production with sunscreen use.

The only limitation of this review was that it didn’t take into account the newer very high protection sunscreens currently being used.

Remember that sunscreen does not fully prevent exposure to sunlight. To get maximum sun protection from a sunscreen one would need to apply 2mg/cm squared and reapply every 2-4 hours. Most people do not wear sunscreen in large enough quantities. Some of the analysis even suggested that there is still enough UV R exposure to produce adequate vitamin D even while using sunscreen.

Interestingly there are some people who do not produce enough Vitamin D even with large amounts of sun exposure, and some people with minimal sun exposure with normal Vitamin D levels. There seem to be as yet unidentified factors influencing Vitamin D synthesis.

More importantly you can get enough Vitamin D from oral supplements and diet without exposing yourself to an increased risk of skin cancer.

Sunscreen and its impact on the environment

UV filters oxybenzone,  camphor derivates, octocrylene, and octinoxate  have caused much recent controversy as they have been shown to accumulate in the water sources of the world and suspected of being responsible for the bleaching of coral reefs. They are not easily removed by conventional water treatment methods. As a result of this several states in the united states have banned these sunscreen ingredients. Of note is that the study that claimed the adverse effects on coral reefs used much larger concentration of oxybenzone than is actually found in even the busiest beaches in the world. However this is certainly a warning and has led sunscreen manufacturers to seeking alternative ingredients in their formulations.

It doesn’t however warrant a blanket boycott of all sunscreens. If anything, there is a shift towards using more physical or mineral blockers in sunscreens like zinc oxide and titanium dioxide which is recommended for sensitive skin and children.

Sunscreen and its relation to Frontal Fibrosing Alopecia

On that note physical blockers or mineral sunscreens have also been controversially linked to frontal fibrosing alopecia which is a condition that is caused by progressive fibrosis of the hair follicles of the frontal hairline resulting in hair loss and a receding hairline. Small quantities of titanium supposedly from titanium dioxide containing mineral sunscreens, have been found in the hair shafts of patients with frontal fibrosing alopecia. There is no conclusive proof yet that the sunscreens are the actual cause for frontal fibrosing alopecia.

Is sunscreen an endocrine disrupter?

Oxybenzone has been identified as an endocrine disrupter affecting the endocrine systems in rats and fish.  But for this to affect humans, one would need to apply an unrealistically large amount of oxybenzone to the skin for decades to absorb the quantities of avobenzone needed to cause any real danger. To date there have been no proven significant negative effects from oxybenzone in humans.

What about SPF ? The burning question is whether a higher SPF provides greater sun protection?

To recap, SPF or sun protection factor is actually only a measure of protection against UVB. An SPF of 30 means that you will be able to stay in the sun 30 times longer without burning, than you would be able to without wearing the sunscreen. This does not equate to 30 min and varies amongst individuals, as we all burn at different rates depending on our skin type.

SPF is measured in a test environment which is nothing like real life.It does not take into account sweating, environmental factors and the varying application by the sunscreen user.

In a test environment sunscreen is applied very thickly, at 2mg of sunscreen per square centimetre which is the minimum needed to get the protection labelled on the sunscreen.

Several investigations  have found that sunscreen users rarely apply sun screen adequately and evenly.The quantity that is actually applied by people is closer to 0.5mg per square centimetre. So we are never really getting the same protection as on the label.

Using a lower SPF sunscreen at quantities lower than 2mg per square centimetre actually reduces the overall sun protection factor.

However a recent study published in the Journal of the American Academy of Dermatologists (JAAD) confirmed that realistic usage of a higher SPF sunscreen of SPF 70 and above may provide enough sun protection to protect against photo ageing and skin cancer.

Another point worth emphasising is that while it is true that SPF15 filters out 93.3% of UVB, SPF30 96.7% and SPF50 98.3%, making it seem that there is very little benefit in using the higher SPF, one needs to consider that only the amount of UV light reaching your skin is important. If you look at it this way then SPF 15 allows 6.7% of UVB to reach your skin while SPF 50 allows only 1.7% of UVB. Its not about what you are filtering out, but rather about what you are allowing to reach your skin.

Why should you consider tinted sunscreen?

Tinted sunscreens containing ‘light reflectors’ protect against visible light which causes erythema in light-skinned individuals and hyperpigmentation in dark-skinned individuals. Visible light is the light that we see and makes up 44 % of the electromagnetic spectrum reaching the earth. Conventional broad spectrum sunscreens do not protect against visible light. For a sunscreen to do this it must be opaque and visible on the skin. The newer generation of physical sunscreens made with nanotechnology use small particle sizes of zinc oxide and titanium dioxide to decrease the “white” appearance of the sunscreen and make them more aesthetically suitable for use. Ironically these fine particles can no longer reflect visible light. Tinted sunscreens containing shades of iron oxide and titanium dioxide in various combination are not only able to blend with different skin tones, but are also able to reflect visible light. In this way they can protect against disorders of hyperpigmentation like melasma, post inflammatory hyperpigmentation and lichen planus pigmentosus.  Iron oxide pigment can also be found in tinted powder or brush on sunscreens which can be conveniently reapplied during the day.

Sunscreens treating early skin cancer

The latest research in sun screen technology has seen the development of a new generation of ‘active sunscreens’ containing DNA repair enzymes. These sunscreens have very high SPF and are in the unique position to be seen as potential treatment of early skin cancer (not melanoma) rather than just preventative treatment like regular sunscreens.  Skin cells have their own mechanisms to repair DNA damage caused by UVR, but with excessive sun exposure these mechanisms are overwhelmed which can lead to permanent DNA mutations causing skin cancer and photo ageing.  Scientific studies have shown that sunscreens containing photolyase and endonuclease can enhance the DNA repair mechanisms in damaged skin cells and reduce the lesions of early skin cancer in sun damaged skin. These novel sunscreens may also protect against photo ageing and prevent the breakdown of collagen in the dermis by decreasing the enzyme matrix metalloproteinase.

Conclusion

The science behind sunscreen technology and skin cancer prevention is by no means stagnant and while new challenges emerge regarding the potential dangers of ingredients, science will continue to forge ahead bringing new solutions and replacing old ones.

At the current time sunscreens remain our best solution to the prevention of skin cancer and photo-ageing.

References

• The effect of sunscreen on vitamin D: a review*
  R.E. Neale iD ,
  1 S.R. Khan,1 R.M. Lucas iD ,
  2 M. Waterhouse,1 D.C. Whiteman iD 1 and C.M. Olsen iD 1

• Population Health Department, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, QLD, 4006, Australia
• 2 National Centre for Epidemiology and Population Health, Australian National University, Australia
• Linked Editorial: Wolf. Br J Dermatol 2019; 181:881–882.

• High-SPF sunscreens (SPF $ 70) may provide
  ultraviolet protection above minimal recommended
  levels by adequately compensating for lower
  sunscreen user application amounts.
  Hao Ou-Yang, PhD,a Joseph Stanfield, MS,b Curtis Cole, PhD,c Yohini Appa, PhD,a and Darrell Rigel, MDd
  Los Angeles, California; Winston Salem, North Carolina; Skillman, New Jersey; and New York, New York

• Photoprotection beyond ultraviolet radiation: A review of tinted sunscreens
  Alexis B. Lyons, MD,a Carles Trullas, MSc,b Indermeet Kohli, PhD,a Iltefat H. Hamzavi, MD,a and
  Henry W. Lim, MDa
  Detroit, Michigan; and Barcelona, Spain

• DNA repair enzymes in sunscreens and their impact on
  photoageing—A systematic review.
  Hanna Luze1,2 | Sebastian Philipp Nischwitz1,2 | Iris Zalaudek3 | Robert Müllegger4 |
  Lars Peter Kamolz1,2

• Review of environmental effects of oxybenzone and other sunscreen active ingredients.
  Samantha L. Schneider, MD, and Henry W. Lim, MD
  Detroit, Michigan