In our final post on sunscreen, we will discuss the proper advice and application of sunscreen to achieve optimal protection from UV radiation.
A recently published study found that, even with detailed guidance and individual instruction, trial participants still applied less than half the amount of sunscreen recommended. Participants who were instructed only by the product packaging used slightly more than a third of the required amount. This is an important gap in public knowledge, as SPF ratings are based on tests carried out with the recommended amounts of sunscreen.
The commonly accepted advice around sunscreen application is that individuals should application of 2mg of sunscreen per square cm of skin. This equates to roughly 30 grams for an adult per application, about a shot glass full. Another measure of this would be to use a quarter to a third of a teaspoon for the face, and one full teaspoon for each limb.
As sunscreens work by being absorbed by the skin (as opposed to zincs which provide a physical barrier) it is incredibly important that sunscreen be applied BEFORE exposure begins. The recommended advice states that 20 minutes is optimal, with studies confirming that 15-30 minutes before exposure provides enough time for sunscreen to be absorbed. The same study suggests that sunscreen then be re-applied 15-30 minutes AFTER sun exposure begins, and then as necessary after physical activities likely to remove it, such as swimming, rubbing, or sweating from exertion.
A problem that may arise from the necessity that sunscreen be applied 20 minutes prior to going out is that the wearing clothing during this period may hamper the effectiveness of the sunscreen once exposure begins. Another recent study found that waiting eight minutes before putting on clothes after applying sunscreen was the minimum amount of time necessary to achieve effective protection from sunscreen during subsequent exposure.
Many cancer councils refer to sunscreen as being skin’s last line of defence. While there are many effective sunscreens available, none provide absolute protection from UV radiation. It is important that other sun smart behaviour be exercised wherever possible, such as wearing UV protective clothing and staying in the shade, particularly in the middle of the day. Interestingly, particular colours of clothing material have been found to provide more UV protection than others, so if contemplating every day clothing as a method of UV protection consider the colour and material. An Industrial and Engineering study found that red and blue provide more protection from UV than yellow, and the more intense the shade, the better the protection.
In a study testing the effectiveness of a mobile phone text message reminder service for the application of sunscreen, 70% of those who weren’t prompted by their phones forgot to apply sunscreen. While 56% of those who received the reminders remembered, and two thirds requested to keep receiving the reminders.
Overall the most important considerations regarding sunscreen are to remember to use it and ensure it is applied properly and regularly.
References;
http://www.ncbi.nlm.nih.gov/pubmed/11712033
http://pubs.acs.org/doi/abs/10.1021/ie9006694
http://www.ncbi.nlm.nih.gov/pubmed/19917951
http://www.ncbi.nlm.nih.gov/pubmed/19845666
http://www.ncbi.nlm.nih.gov/pubmed/19775354
http://www.ncbi.nlm.nih.gov/pubmed/19747242
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