The short answer: Bioavailability in skincare means how much of an active ingredient reaches the part of the skin where it’s meant to work. It depends on two things: whether the ingredient is still potent when you apply it, and whether it can get past the skin barrier. A high percentage on the label doesn’t guarantee either.
The percentage on the label tells you what went into the bottle.
It doesn’t tell you how much is still active when you use it. And it doesn’t tell you how much gets past the surface of your skin.
That gap has a name, borrowed from pharmacology: bioavailability.
What does bioavailability mean in skincare?
In medicine, bioavailability describes how much of a drug reaches its site of action. Skincare has borrowed the term to ask a similar question: of the active ingredient in this product, how much reaches the skin layer where it can do its job?
For a hydrating ingredient, the target might be the surface. For a peptide meant to signal collagen-building cells, the target is the dermis. The deeper the target, the harder the trip.
What stops skincare ingredients from working?
We think of it as two separate delivery problems. One happens before the product touches your skin. The other happens when it gets there.
| Problem | When it happens | What goes wrong | Example |
|---|---|---|---|
| Degradation | In the bottle, before use | Actives break down after contact with water, oxygen and light | Vitamin C turning brown over time |
| Barrier penetration | On the skin, after use | Actives can’t cross the stratum corneum in meaningful amounts | Large peptides sitting on the surface |
Most brands address one, if either. The label addresses neither.
Why is the skin barrier so hard to get through?
The stratum corneum, the outermost layer of skin, is about 10 to 20 microns thick. It’s made of flattened cells held in a waxy, oily matrix, and it’s excellent at keeping things out.
Dermatology’s rule of thumb is that molecules above about 500 Daltons don’t cross intact skin in meaningful amounts. Many of the most interesting skincare actives are above that line. The 500 Dalton rule, explained.
What’s the difference between topical and transdermal delivery?
Topical delivery aims to get an ingredient into the skin and keep it working there. Transdermal delivery aims to get a drug all the way through the skin and into the bloodstream, like a nicotine or hormone patch.
Skincare should be topical. The goal is to reach the right layer of skin, not the rest of your body. But skincare can learn a great deal from transdermal drug research, because pharmaceutical scientists have spent decades on the same core problem: how to move a molecule across the skin barrier without damaging it.
How do skincare ingredients get into the skin?
There are several approaches, each with trade-offs.
| Approach | How it works | Trade-off |
|---|---|---|
| Choose small molecules | Use actives already under ~500 Da, like caffeine or lactic acid | Limits you to a narrower set of ingredients |
| Modify the molecule | Add a fatty-acid tail (palmitoyl peptides) or a sugar (glucosyl hesperidin) to change how it behaves | Usually makes it heavier |
| Chemical penetration enhancers | Solvents, fatty acids or acids that loosen the barrier | Can irritate, especially around the eyes |
| Encapsulation | Wrap the active in a shell, like a liposome, to protect it and release it over time | Built mainly to protect the active; doesn’t necessarily carry it deeper |
| Devices | Microneedling or iontophoresis (a mild electric current) | Requires a tool or treatment |
| Carrier systems from drug delivery | Solvent and carrier systems designed to keep actives dissolved and move them across the barrier | Newer to skincare; ask for data |
Is encapsulation the same as a delivery system?
Not quite. Encapsulation is mainly about protection: keeping an active stable until it’s released. A delivery system is about transport: helping the active travel past the barrier.
Both can be useful. They solve different problems. When a brand says “encapsulated,” it’s fair to ask which problem they’re solving.
How Exponent approaches bioavailability
We’ve built one technology for each delivery problem.
Patented Powder Dosing addresses degradation. Our Activated Serums keep vulnerable actives like Vitamin C and Retinol dry and precision-dosed until you use them. You activate each dose fresh.
Active Ion Delivery addresses barrier penetration. It’s a carrier system licensed from pharmaceutical drug-delivery research, invented by Dr. Eric Fossel, a Harvard Chemistry PhD and Professor at Harvard Medical School who holds about three dozen patents. It uses charged ionic carrier molecules in a non-aqueous system designed to keep actives dissolved as they cross the stratum corneum. It isn’t a device and doesn’t use electric current.
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| Six bioavailable actives, one pharma-developed delivery system, and nine clinically measured under-eye results. SHOP NOW: Needle-Free Lifting Eye Cream |
In comparative artificial skin-membrane testing, the carrier delivered 39 times more active molecules across the barrier than the identical formula without it.
Its first skincare use is Needle-Free Lifting Eye Cream, where it’s paired with larger actives like peptides and Glucosyl Hesperidin. In an independent six-week clinical study of the finished eye cream with 30 participants, all nine measured under-eye parameters improved with statistical significance, including 100% of participants showing improvement in dark circles and elasticity. How we chose the actives.
One keeps the active potent. The other helps it get where it needs to go.
FAQ
What is bioavailability in skincare? It’s how much of an active ingredient reaches the part of the skin where it’s meant to work. It’s affected by both stability in the bottle and penetration through the skin barrier.
Is transdermal delivery safe in skincare? Skincare aims for topical delivery, into the skin rather than through it into the bloodstream. Transdermal drug research informs how skincare carriers are designed, but the goals differ.
Does a higher percentage mean better results? Not necessarily. A higher percentage doesn’t help if the active has degraded or can’t get past the barrier.
What are penetration enhancers? They’re ingredients or methods that help actives cross the skin barrier. Some work by loosening the barrier, which can cause irritation in sensitive areas.
Is Active Ion Delivery the same as iontophoresis? No. Iontophoresis uses a device and electric current. Active Ion Delivery is a carrier system built into the formula itself.
Sources
- Bos JD, Meinardi MMHM. The 500 Dalton rule for the skin penetration of chemical compounds and drugs. Exp Dermatol. 2000;9(3):165-169.
- Clinical study EXB 25-13, Innovia Research Labs. N=30, 6 weeks. Expert grading and instrumental measurement. Results reflect the full formula, not individual ingredients. Individual results may vary.
- 39X figure: Internal study, November 2025, comparative permeability across validated artificial skin membranes. Data on file at Novilla Pharmaceuticals.
- Patented Powder Dosing: US Patent 12,201,951 B2.
