In any pharmacy such as Boots or Superdrug, there will likely be hundreds of sunscreen products on offer in different brands and showing different numbers on specific products. These numbers refer to the level of sun protection factor and can range from very low such as factor 8 right up to factor 60, which offers all-day protection.
Understanding Sunscreen SPF Numbers
The sun protection factor number is a useful indication of the level of protection that each product is able to provide. It is well worth asking a pharmacist for advice on specific brands and which are most suitable to meet individual skin types. A simple rule of thumb is that the paler the individual's skin tone is, then the greater the sun protection factor that is likely to be required in order to prevent sunburn and more severe forms of sun damage which may result in melanoma or other forms of skin cancer.
SPF numbers have two main uses, including:
- to calculate minimal erythema dosage
- to indicate absorption percentage of UVA radiation
Minimal Erythema Dose
The minimal erythema dose or MED is used to provide the individual with a measure of the length of time one may be exposed to sunlight before the skin begins to show the early signs of sunburn where the skin starts to appear very slightly pink in colour. It is the SPF number that is multiplied by the MED to work out this amount of time. An example of this is if one takes 20 minutes of exposure to the sun before exhibiting the earliest stage of sunburn, then wearing a sunscreen offering sun protection factor 10 would mean that one could remain in the sun for approximately 200 minutes before showing signs associated with sunburn.
However, if one is swimming or engaging in active sport, then even if water-resistant sunscreen has been used it will be necessary for sunscreen to be reapplied afterwards.
Selecting Appropriate Sunscreen
It is worth taking time to consider which sunscreen is going to be most useful rather than just purchasing the nearest item or those on special offer. This is because different products offer very different levels of protection and are useful for various situations. Sunscreen must be broad-spectrum in order to protect one against the damaging effects of both UVA and UVB levels of radiation. Purchasing a sunscreen with an SPF number of at least 15 or ideally 20+ is advisable. Also, think about whether one is likely to be involved in water-sports and if this is the case, ensure the sunscreen is labelled water-resistant.
As highlighted above, SPF numbers are used to show the level of protection offered by a particular type of sunscreen. When multiplied by the MED, it is possible to identify roughly how long one may be exposed to sunlight before exhibiting early signs of sunburn. If in doubt it is always better to purchase sunscreen of around 20+.
Source:
McClay et al. (2004) 100 Questions and Answers About Melanoma and Other Skin Cancers Massachusetts: Jones and Bartlett
Kate Le Page - Kate Henning-Le Page writes about eating disorders, body image and recovery issues. She specializes in anorexia recovery.
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