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HDRS – a new method for SPF-Determination

On the way to ISO standard!

For more than 20 years, ISO 24444 has been the “Gold Standard” for measuring the sun protection factor (SPF) in vivo. The SPF is determined on basis of an erythemal skin reaction after UV irradiation. This value is the central labeling element of sunscreens, which offers consumers safety when spending time in the sun. Hybrid Diffuse Reflectance Spectroscopy (HDRS) is a new, alternative non-invasive in vivo/in vitro method that works without any harmful UV radiation. HDRS a method which is in no way inferior to ISO 24444 in terms of reliability and practical relevance and offers further advantages, too. Dr. Schrader Institute played a key role in the development of the HDRS method and has been a member of the ALT-SPF consortium (, which deals with the comparative evaluation of alternative SPF test methods, since 2021.

The new HDRS method reached the status of “Final Draft International Standard” (FDIS) in June 2024 as ISO 23698 and cleared the penultimate stage before being established as a new ISO standard. HDRS is characterized by the following advantages:

The method of the future – already at Institute Dr. Schrader!

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