Hyaluronic acid is a skin care ingredient that isnt going anywhere soon.

The trendy beauty staple is said to hydrate, plump and protect the skin from moisture loss, and is the key ingredient in products from drugstore and budget-friendly brands like Neutrogena ($21) and cult favorite The Ordinary ($7) to prestige lines like Dr. Barbara Sturm, a brand that sells a 30 ml bottle of hyaluronic acid serum for $300.

With all of the hype around this moisture-boosting ingredient, consumers find it challenging to understand which products give the best results. But thanks to beauty communities on Reddit , Makeup Alley and Sephora message boards , skin care lovers can share what is and isnt working for them.

One of the top questions on the message boards discussing hyaluronic acid is, Is it worth it? Does it really make a difference whether you purchase a $7 product or upgrade to a $300 serum? We talked to dermatologists to find out.

What is hyaluronic acid, anyway?

Hyaluronic acid is a natural sugar found in our skin, said Joshua Zeichner , director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York. It is what provides bounce and plumpness to the skin. Think of it like the stuffing in your mattress. As a humectant, hyaluronic acid is essentially a sponge that binds to 1,000 times its weight in water.

Even though the humectant is a powerhouse, that doesnt mean it can do it all.

When it comes to fully moisturizing and plumping your skin, hyaluronic acid alone might not do the job, said Victoria Fu, who is half of the chemist duo at skin care brand Chemist Confessions . Look for products that pair with other types of hydrators such as glycerin, glycols, urea, panthenol, sodium PCA, etc. One ingredient wont solve all your moisturizing troubles skin hydration is a team effort.

Why are some hyaluronic acid products so expensive?

What drives up the cost of hyaluronic acids? A few things: molecular weight, added ingredients and product packaging.

There are some studies that suggest smaller molecular weight HA can penetrate somewhat better and can have long-term anti-aging benefits on top of hydration, Fu said. The Ordinarys $7 HA formula combines low, medium and high molecular weight hyaluronic acid, while Dr. Sturms $300 HA uses short- and long-chain molecules (low and high weight). For those of us who werent paying attention in chemistry class, Zeichner kindly breaks the science down for us.

Smaller molecules can better penetrate through the outer skin layer to give more of a plumping effect, Zeichner told HuffPost, explaining that the smaller molecules can go deeper into the skin. Long-chain HA, because of its large size, does not penetrate well through the skin and provides a hydrating effect to the outer skins layer. Zeichner says many over-the-counter products stick to high and medium molecular weights because there is some data that low molecular weight HA may actually promote inflammation in the skin.