Good measurement practice matters Clinical sun protection product testing update


Stephan Bielfeldt*, Christiane Röck, Marianne Brandt, Klaus-Peter Wilhelm
*Corresponding author
proDERM GmbH, Schenefeld-Hamburg, Germany


Whilst light emitted to the earth is essential for life, overexposure to it can cause many adverse effects leading to premature actinic skin aging, photo-dermatoses, and even skin cancer. Due to the increase in the incidence of skin cancer and the public concerns  of ozone layer depletion, more attention is being placed on protecting the skin from the sun‘s ultraviolet rays with broad spectrum sunscreens, as well as developing other prevention strategies. As described herein, since sunscreen products provide an important protective function they should always be tested with due care, using accurate and validated methodology. If an imprecise method is used in sunscreen testing, this can lead to a misunderstanding of the protective function and result in considerable damage to both consumers and producers. It is therefore understandable that a labeled SPF that is based on a wrong measurement might have significant impact on the sales figures, brand image and might even lead to indemnity claims. Therefore, the quality and the accuracy of the measurement methods in particular, are critical. In addition due care must also be given to those methods used for evaluating the longevity of sunscreen protection when exposed to instances of water, sand and sporting activities.


Contrary to scientific fact, many people continue to believe that constant exposure to sunlight is beneficial to their general well-being and despite warnings about the dangers, most enjoy relaxing in the sun. Whilst sunlight does have many advantages, exposure to the skin may result in premature actinic skin aging, pigmentary changes, photosensitivity reactions and increased incidence of skin carcinogenesis (1). Therefore, the need for reliable sunscreen protection, to reduce the damaging effects of ultraviolet (UV) radiation to the skin cannot be dismissed (2).


Sunburn is inflammation of the skin caused by actinic rays from the sun or artificial sources (1-3), and severe exposure may result in erythema, blisters and pain. As ultraviolet rays penetrate the dermis, they break down collagen and elastin, the two main structural components of the skin, a process that results in the wrinkled appearance of sun-damaged skin (4). In addition, the sun damages the DNA of the exposed skin cells. In response, the cells release enzymes that excise the damaged parts of the DNA and encourage the production of replacement DNA (5).