Conclusion
On the sunny side of the street
Sunscreens have come a long way since the long-forgotten Benjamin Greene, a pilot in the second world war and later a pharmacist, developed Red Vet Pet. His thick, red liquid concoction—apparently with a similar viscosity to petroleum jelly—had limited effectiveness but got the orb rolling. The jelly was later remarketed as Coppertone.
The new formulation gained commercial momentum with a long-serving image of a playful dog pulling down a small, pigtailed girl’s bikini bottom with his teeth. The girl turns round to see her white backside contrasting with a deep sunburn. Underneath were the words Coppertone. The message was pretty straightforward.
Decades later, sunscreen is more common than ice-cream vans at a fiercely radiated beach. That isn’t to say the myriad tubes and bottles of UV protection are all effective. And although the knowledge of skin cancers and conditions arising from sun damage has risen steeply, it appears to be contained in a few cloisters.
You might think that communicating something as simple as good use of sunscreen wouldn’t be too difficult. That is, until you read up on what is screened or blocked, the protection factors, and how much sunscreen you should rub on.
Most people use too little. They squirt a small coin’s size onto their hands, spread it over their face followed by a few dollops on their body.
The International Agency for Research on Cancer of the World Health Organisation emphasizes the importance of applying the correct quantity of sunscreen for the sun protection factor claimed. The “correct quantity” is based on the amount used for testing sunscreens—2 mg/cm2, which a European Commission paper assures me equates to six teaspoons of lotion (about 36g) for the body of an average adult.
Then there is the question of how often this needs to be repeated. As you probably know, it should be reapplied every two to three hours, after swimming, or to top up while wilting in the heat. What you probably didn’t know is that, according to research at the University of California, Riverside, sunscreen must be reapplied within two hours. If it is not, the single application would be worse than not applying it at all, owing to the release of extra free radicals from the sunscreen’s chemicals absorbed by the skin.
Assuming a good coating and correct reapplication, is the screen up to the job in the first place? To be effective, sunscreens have to protect us from UVB and UVA radiation. Sunburn arises from insufficient protection from short UVB radiation; premature ageing of the skin is caused by UVA radiation; excessive exposure to both impacts on the body’s immune system.
No sunscreen product can filter all UV radiation, nor is there conclusive evidence that sunscreens protect us from melanoma or basal cell carcinoma (don’t take our cartoon literally). But to ensure a broad protection, screens should filter out wavelengths of 370nm.
Sun protection factors (SPFs) are not easy to digest either. The increase in protection is only linear in the case of sunburn so that an SPF of 30 is twice as good as 15 but filters only 97% of UVB radiation compared with 93% for SPF 15, and SPFs greater than 50 do not significantly increase protection from UVs.
Overuse of sunscreen is considered bad, too, as this is seen to deprive the body of much-needed UV, which of course provides us with vitamin D. But I can’t really take this seriously. Assuming commonsense, even in the most sun-starved regions of Britain, correct use of sunscreen, a proper diet and a few supplements should provide enough vitamin D.
No one Is suggesting that the public paints sunscreen on in thick, broad strokes. Good practice will grow as better advice is given. You can start by suggesting to your own patients how much sunscreen to use, when it should be reapplied, and give a concise account of what it does. Our report on sunscreens might even help you with your own recommendations.
