Your skin barrier, explained

Skin is a protective barrier, and a selective one. Understanding how it is built makes patch science easy to follow.

A useful way to picture the surface

The outermost skin layer, the stratum corneum, is often compared with a wall: closely arranged cells surrounded by layers of lipids, or fats. This structure helps resist the passage of substances from outside. Laboratory research by Bouwstra and colleagues, published in March 1995, examined the organisation of these lipids in a reconstructed skin model.

Hair follicles are part of the skin’s structure too, and researchers study their role. Otberg and colleagues’ human caffeine research is one example.

What researchers look at

Molecular size and how a substance distributes between watery and fatty environments are two of the properties researchers study. Potts and Guy explored their relationship with skin permeability in a 1992 analysis, work that helps explain why each ingredient behaves in its own way. Read the original permeability paper.

The surrounding formulation matters too, which is why medicinal patch guidance considers formulation alongside release, adhesion and skin permeation. The EMA’s 2014 guideline explains these development questions.

Size is one part of the story

Molecular size is one useful property. The chemical form, the formulation around it and the hours it spends against the skin all count too.

That is why a 24/sync patch is built as a whole: the actives sit in the adhesive layer that touches your skin, designed to release steadily across the wear time.

What a good patch label shows you

The exact ingredient names, the amount of each, the wear time and clear instructions. A 24/sync label lists every ingredient and amount, down to the milligram.

Keep science separate from application instructions

The science is the background; the directions are the routine. Use the directions supplied with the product for placement, wear time and preparation, rather than choosing them from a research paper. Our patch guide is the place to start for practical information.

If your question is whether a patch suits your routine, start with its instructions and ingredients. For more of the science, see how patches are tested and our Science & standards page.