We heard about a consumer myth that needs busting from @meltam. Do sunscreens really last four hours in normal use?
Let us know your answer in the comments below and enter our competition.
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Donāt think so. If the sunscreen isnāt rubbed right in to skin thoroughly you havenāt had it onfor 20mins been before exposure, it will last about an hour. Seems to beshort lasting im the ocean. Sunshirts are better and bring zinc cream back.
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Maybe an additional question could be ā¦does towelling oneself after a swim or wiping off sweat cause the sunscreen to be removed?
Or, why does sunscreen make my clothes go orange?
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I only use Zinc cream, it lasts all day, in fact it is rather difficult to remove! I generally only use it on my face when out in the sun for extended periods on a mountain bike ride, my arms are covered by clothing. Otherwise when out in the sun I use a wide brimmed hat and long shirt sleeves.
Other types of sunscreen tend to diminish when sweating a lot- my wife forgot her hat on a job this week and was suffering from the sunscreen she applied running into her eyes. Clearly if it was in her eyes, it was no longer on her forehead! That was happening well before an hour of working outdoors in the heat (33C)
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I agree with your previous comment re clothing - Nothing beats it, and Zinc for the few areas that canāt be covered easily. Sweat not only gets it into eyes, but can affect grip and other things - grip on handlebars, and I have some āsporting equipmentā that requires a firm decisive grip under a lot of hand pressure (80 pounds) - very dodgy with slippery hands. Thereās some fairly good breathable/loose fitting stuff around these days, but often the old faithfuls work just as well. Even at the beach things like rash vests/etc ā¦ just not sure I trust sunscreen, whats in it, how well it works, etc - maybe just random paranoia, Iām fine with that 
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How do you keep them up? 
Sorry I tried but I just couldnāt resist.
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What is ānormal useā, I am sure that varies by whom you ask. Is there a definition of normal use that is the standard for these claims?
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Normal use could be swimming, outside activity like sports, sunbathing - I suppose weāre saying ānormalā just to cover off any extremes, although Iām not sure what an extreme use of sunscreen might look like!
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Then my answer would be yes they would last 4 hours in normal use but would not be as effective as when first applied and waiting 20 minutes before sun exposureā¦
There are two different things being tested. One is Sun Protection Factor (SPF) which is the difference in time that it takes for unprotected (UP) skin and skin with Sun Protection (SP) to redden. For example if skin with SP took 500 minutes to redden and UP skin took 10 minutes in standard levels of Ultra Violet Radiation (UVR) then the SPF of the SP would be 500/10 = SPF 50
The other is, does the SP last when immersed in water for the products claimed water resistant time eg 4 hours
The Cancer Council of Australia published the following on their web site:
āWater resistant: Does not come off the skin during swimming or exercise, provided it is not wiped off. While a label may state a sunscreen is ā4 hours water resistantā, sunscreen still needs to be applied every two hours to maintain the same level of protectionā
From the TGA web site:
"Many sunscreens are designed to be used while swimming, surfing or participating in other water sports.
Water resistance is measured by determining the SPF measurement after the period of water immersion claimed on the product. For example, a product with 2 hours water resistance was tested for its SPF after the product was applied to the skin and immersed in water for 2 hours.
Water resistant products still need to be reapplied regularly due to being worn or rubbed off, e.g. during towelling dry.
The criterion for the āwater resistantā claim is essentially unchanged for SPF 50+ products. The maximum water resistant claim period of 4 hours is only allowed for products which have SPFs of 30 or more after immersion in water."
From further reading of the test standard (Standards Australia, Standards New Zealand. Australian/New Zealand Standard AS/NZ 2604 (Sunscreen products - evaluation and classification). Sydney, Australia; 2012.) a reference by the TGA (Theraputic Goods Administration) states:
"directions for use of the product
Note: The directions for use for a primary therapeutic sunscreen should include statements to the effect that the product should be applied to the skin in generous amounts over all of the exposed areas 20 minutes before sun exposure, it should be reapplied every two hours or more often when sweating, and should be reapplied after swimming or towelling. The labelling must not contain a claim (for example, āall day protectionā) that indicates or implies that the product does not need to be reapplied at regular intervals."
So it should still be on the skin after 4 hours of exercise, sweating or swimming, but mechanical means will remove it eg wiping with a towel, rubbing on a shirt. But regardless, to maintain the same level of protection as stated on the container re-application at least every 2 hours is required. This does not mean a person will not get burning/reddening it only increases the time it takes before burning/reddening will occur.
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As a person who inherited the very pale skin of my Scottish forefathers, I can say that it seems to widely depend on what your activities are. If I am sitting still in the sun enjoying a BBQ or watching the Aussies cheat at cricket, the sunscreen of a reputable brand seems to last as long as it states on the bottle (as in I get home and no burnies/blisters the next day for me). If I am actually doing something physical such as playing sport, working in the garden, running around with the kid, etc. then the protection value appears to be halved. If I put on a 4 hour protection and donāt reapply after 2 hours Iāll be a very sore boy in the morning.
I feel the same goes for the water resistant claims. I do notice however the wording posted above āafter immersion in waterā, which means that to prove your claim you could throw on the sunscreen and then hold your arm under water for 2 hours - job done. This gives a false impression to people who are down at their local surf beach getting dumped by the waves and tumbled around in salty, sandy water. Iām fairly sure Standards Australia do not test water resistant sunscreens under those conditions.
Raises an important point though - should testing standards used by the authorities reflect what could be termed ācommon usage scenariosā for products? In a country with a large beach culture you would fairly expect that when purchasing a water resistant sunscreen it would last the stated time under those conditions experienced at the beach, or water-skiing, white water rafting, etc. In the end though Iāve found over many years that the best protection is multiple, the old Slip, Slop, Slap promo should be on throughout the year (yes Iāve sometimes had worse burns in winter than summer). I put sunscreen on even under my clothes as Iāve found having some fabric covering you is no protection unless itās rated as such - getting blisters under a t-shirt hurts, especially when they burst and stick lol.
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Water resistance testing takes place on (paid) volunteer subjects in a spa pool. After having the sunscreen applied to their back, the subjects spend a total of four hours in there, with the spa jets on for about 20% of the time (a few minutes at a time). The four hours also includes short ārestsā outside of the spa pool, though they canāt towel off. They can read, watch TV etc but basically just sit. When the four hours is up, they are air-dried then have the solar simulator to test the effectiveness of the sunscreen.
So youāre right, itās not exactly ātypicalā water activity, thereās no getting tumbled in surf, rubbed with sand, towel drying etc.
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