UPF Standards Were Written for Textiles, Not Sun Patches

An August 2026 review in the Journal of Drugs in Dermatology suggests that ultraviolet protection factor, or UPF, labeling could make adhesive sun patches easier to assess. The idea is understandable. But UPF is not a generic badge for anything solid that blocks sunlight. The standards behind it were written for textiles.

What the UPF standards cover

AATCC Test Method 183, in its 2020 edition, measures ultraviolet radiation transmitted or blocked by textile fabrics, in dry or wet conditions. ASTM D6603 governs labels on ultraviolet-protective textile products and ties those labels to the AATCC method. Its framework accounts for specimen preparation and expected consumer wear, with the lower qualifying value generally carried to the label.

Neither published scope names silicone adhesive film. That does not prevent a standards body from developing or validating a suitable method. It means that putting UPF on a sun patch would require more explanation than the familiar number supplies. The review's suggestion is a proposal, not evidence that current patch claims already follow the textile workflow.

Where the SPF 100 result came from

The strongest figure cited for patches traces to a paper first published on February 22, 2021. Researchers at the Technical University of Denmark made an experimental silicone and glycerol adhesive with titanium dioxide, mounted samples on polyurethane backing, and measured ultraviolet transmission. At the higher titanium dioxide loading, transmission stayed below 0.5 percent across UVA and UVB wavelengths, producing a calculated SPF of 100. The value remained 100 after 20 hours at 80 percent relative humidity.

That is useful materials evidence, but it is not the U.S. Food and Drug Administration's SPF test. The FDA method is an in-person sunburn test with valid results from at least 10 people. Its separate Broad Spectrum test measures UVA and UVB performance on prepared plates.

The patch result therefore fits neither familiar consumer pathway cleanly. It does not show that patches fail. It shows why a retail label should identify the test method, the finished sample tested, and what happened after moisture, movement, edge lifting, and reuse.

Questions worth carrying forward

• Was the finished patch tested under a published standard?
• Does the reported number cover both UVA and UVB?
• Were adhesion and protection measured together during wear?

Sources: Technical University of Denmark · U.S. Food and Drug Administration · AATCC · ASTM International