Hydrogel under-eye patches with hyaluronic acid, from Natura Siberica's Dyal line. Fifteen to twenty minutes.
What hyaluronic acid actually is
Not an acid in the sense that matters in skincare — it does not exfoliate, it does not sting, and it has nothing in common with glycolic or salicylic acid. It is a humectant: a molecule that binds water and holds onto it, and it occurs naturally in your skin, your joints and your eyes.
It is very good at its job. A hyaluronic acid molecule can hold many times its own weight in water, which is why it appears in almost every hydrating product on the market.
The thing nobody tells you about it
This is worth knowing and it changes how you should use any hyaluronic product.
A humectant pulls water towards itself — from the air if the air is humid, and from the deeper layers of your own skin if it is not. In dry conditions, hyaluronic acid applied to the skin and left uncovered can end up drawing moisture upward and outward, and leaving your skin drier than before. People who find that hyaluronic serums make their skin feel tight are usually running into exactly this.
The solution is simple: always seal it in. Apply hyaluronic to slightly damp skin, and follow it with a cream or an oil that stops the water escaping. A patch does this for you automatically — the hydrogel is both the water source and the seal — which is why patches are one of the better ways to use hyaluronic acid. But do apply an eye cream afterwards.
Getting the most from them
Chill them — cold does more for morning puffiness than anything in the serum. Fifteen to twenty minutes, not longer: once a patch dries it begins taking water back. Do not rinse — tap the remaining serum in, then apply your eye cream.
Note
Single use. External use only — avoid direct contact with the eye. Patch test first if your skin is reactive.