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Sunscreens and Cancer Prevention

May 30, 2012

Anyone who has ever suffered sunburn will attest to the fact that too much sun is not ‘healthy’.

Anyone who has neglected to rub their sunscreen in evenly can attest to the fact that while the handprint on the back is NOT a good look is does prove that the properly spread sunscreen was working.

And anyone who usually burns when doing the coffee run will feel the benefit of their SPF 30 plus in the form of up to five hours of ‘play time’.

Sunscreens do work.

The best types of sunscreens ‘turn down’ the sun across the entire photo biologically active UV range.  The term for this is ‘broad spectrum protection’.   This chemical dimmer switch when applied correctly acts like a veil across the skin, shielding it from the suns energy by either chemical or physical means.  In tech speak we say that they change the quantity rather than the quality of the sun.

Any sunscreen testing facility or fair skinned person (Fitzpatrick skin type 1-3) could demonstrate the effectiveness of a sunscreen in delaying burning simply and relatively quickly and so it is not surprising that sunscreens are an integral part of the global ‘skin cancer prevention’ strategy.  And so why then are so many people questioning sunscreens ability to protect us from cancer?

The answer is that they don’t. Sunscreens have not been proven to protect us from skin cancer – well, not for all types anyway.

Wearing sunglasses and sunscreen is all part of a sensible sun-smart strategy but it doesn’t guarantee you a cancer free life.

Excessive sun exposure, especially when it leads to blistering, burning or the increased development of nevi (moles) are known contributing factors to many types of skin cancers.  That is not the same as saying that they prevent skin cancer – a fact that many journalists neglect to mention.

Sunscreens have been shown to reduce the risk of squamous cell carcinoma and actinic keratosis.  However, basal cell skin cancers and melanoma do not share the same link.

It is important to consider the reality of a situation before passing judgment, as it is often somewhat different to the scientific perception. Here are some reasons why it is difficult to make find an explicit link between sunscreen testing and cancer prevention.

  • It is rare that sunscreens are applied optimally at the right thickness, frequency and time before first exposure.
  • It can take some years before skin damage shows up after excessive sun exposure.
  • It is unethical to burn people intentionally and so much evidence is retrospective in nature and anecdotal.
  • It is difficult to screen out for other compounding factors.
  • It is human nature to forget about something that isn’t happening therefore sunscreen wearers often stay in the sun until they start to burn.  While this is typically longer than their non-sunscreen wearing self the biological effects will be the same once the MED is reached.
  • Many forms of skin cancer have a viral component that trips the balance making sunlight a secondary or contributing factor.
  • Genetic faults have been identified that prime some people for skin cancer while others have no such problem. Again this leaves sun exposure as only a contributing factor.
  • Some of the older studies tested sunscreen products that don’t meet the broad-spectrum requirements.  Changing the quantity not quality of sunlight is of vital importance as our bodies evolved under this spectrum. Blocking half of it is like transporting us to another planet.

In summary it is right to think of a broad-spectrum sunscreen as being an important part of an anti-cancer strategy. However, to assume that this means that wearing sunscreen will prevent the development of all skin cancers is a vast over-estimation

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