Do your skincare ingredients actually reach your skin? The uncomfortable truth about absorption, the 500 Dalton rule, and why delivery systems matter.
Here's an uncomfortable truth: many of the ingredients you pay premium prices for never actually reach the layers of skin where they could make a difference. Your stratum corneum—designed to keep things out—doesn't discriminate between toxins and your $200 serum.
Most large molecules sit on the surface
Some penetrate poorly without help
Small molecules with right delivery systems
A Dalton (Da) measures molecular weight. The widely-cited "500 Dalton rule" suggests that molecules above 500 Da cannot penetrate intact skin. Below 500 Da? Fair chance of getting through. This rule comes from pharmacology research and has been adapted (sometimes misapplied) to skincare.
The 500 Da rule is a guideline, not an absolute. Other factors matter: lipophilicity (fat-solubility), charge, skin condition, and formulation. A damaged barrier lets larger molecules through. An optimized delivery system can ferry large molecules across.
Let's look at popular skincare ingredients and their molecular weights. The results might surprise you.
Yes, but not how you think. Standard HA sits on skin's surface, drawing moisture from the air (good) or from deeper skin layers (bad in dry climates). It works as a humectant on the surface, not by penetrating.
Low molecular weight HA (under 50,000 Da) can penetrate slightly better, and hydrolyzed HA fragments are even smaller. But even these don't reach the dermis where your body produces HA naturally.
Smart formulation can bypass the 500 Dalton limitation. Here's how advanced delivery systems work—and which ones actually have evidence behind them.
Tiny spheres made of lipids (fats) that encapsulate ingredients. Because they're lipid-based, they can merge with your skin's lipid matrix and release their cargo deeper.
Even smaller than liposomes (under 100nm), nanoparticles can penetrate deeper. They're used to deliver sunscreen filters, antioxidants, and anti-aging ingredients.
Ingredients are coated in a protective shell that breaks down on skin contact or over time. This protects unstable ingredients (like retinol) and allows controlled release.
Ingredients that temporarily disrupt the stratum corneum to let other ingredients through. Examples: propylene glycol, ethanol, oleic acid, certain surfactants.
Disclaimer: This article is for educational purposes only and is not intended as medical advice. The information presented is based on generally accepted skincare science, but individual results may vary. Always consult a board-certified dermatologist or healthcare provider before making changes to your skincare routine, especially if you have existing skin conditions.
Our quiz recommends products with proven penetration and effective delivery systems—no gimmicks.
Take the Skin QuizContinue your skincare education with these related guides
Understand the stratum corneum—the gatekeeper to ingredient penetration.
Read MoreWhich anti-aging ingredients can actually penetrate and make a difference.
Read MoreAdvanced delivery systems and innovations in ingredient technology.
Read More