Recently, I read an article that stated that facial sheet masks are one of the fastest-growing segments of skin care (NPD Group, 2014). According to Karen Grant, vice president and senior global industry analyst at the NPD Group, “Masks attract today’s consumers with the promise of immediate results in treating a variety of skin flaws…New formats and formulations that address individual needs appeal to the consumer looking to try something different without spending a fortune.”

These masks are definitely becoming more popular, but do they work? Here, I’ll research the differences between masks and identify what you should look for — and avoid — in a facial sheet mask:

1.) There are four different types of mask material. From worst to best: fiber, pulp, hydro-gel, and biocellulose.

There are four main different types of material that masks are made from, each with its own strengths and weaknesses.

Fiber (cotton) masks have the advantage that they are inexpensive, sometimes as low as $4 or less. Unfortunately, fiber masks also have a limited capacity to deliver ingredients into the skin, do not bind to the contours of the face well, and, well, quite frankly, it’s hard to move in them. You can identify a fiber mask because it will feature a non-woven fabric with a coarse texture that feels and behaves like paper.

Pulp masks generally are in the $4-8 range, and you can identify them by descriptors like “rayon cellulose” or something similar on their labels. Pulp masks have the advantage that they are still inexpensive, and they have better absorption properties than fiber masks. The disadvantages to pulp masks are that they do not allow the user to move very far while wearing one and they tend to dry out quickly.

Hydro-gel masks are typically about $10 each. Called “hydro-gel” because multiple water-soluble (“hydro”) layers of ingredients are blended until they form the consistency of a “gel,” hydro-gel masks generally have two-part systems, with top and bottom halves applied separately. Hydro-gel masks have the advantage that they have excellent absorption properties and will contour well to the skin. The only issues with hydro-gel masks are that they are more expensive than fiber and pulp masks, and it is still hard to move around in them.

Bio-cellulose masks are generally $10 and above. Originally manufactured solely for medical applications to treat burns and chronic wounds, biocellulose is actually an all-natural material, produced through cultured bacteria. The material adheres to the skin tightly, so not an inch of skin is missed, and the absorption properties have been proven to deliver key ingredients deeply into the skin, like the antioxidant coenzyme Q10 (Life Sciences, 2008) and hydrator glycerin (European Journal of Pharmaceutics and Biopharmaceutics, 2014). Bio-cellulose masks also allow you to move around for lengthy amounts of time, unlike the other classes of masks.

2.) With masks, for best efficacy, you need ingredients or delivery systems that enhance the penetration of key ingredients into the skin.

There are many things that will enhance the penetration of ingredients into the skin. As I’ve discussed on the blog before, it is vitally important that you actually make sure that ingredients can get into your skin! For instance, if an ingredient is embedded in a thick layer of petrolatum, it will not get into the skin as deeply as if it were embedded in, say, a mix of glycerin and propylene glycol.

There are several factors that will increase the penetration of key ingredients into the skin: solvent, charged particles called ions, supersaturated solutions, liposomes, vesicles, smaller size of particles in general, and application of techniques like ultrasound (Current Drug Delivery, 2005). For best efficacy, when dealing with masks, look for all of the anti-aging ingredients you normally do (e.g., retinoids, AHAs, antioxidants, B vitamins, peptides), plus either ingredient penetration enhancers, like glycols, and/or microncapsulation and liposomal delivery systems.

And if you are concerned about the safety of penetration enhancers like glycols, rest assured: Glycols are safe in the concentrations they are used in skin care and cosmetics. The internet rumor started about five years ago, when people misinterpreted the Material Safety Data Sheet (MSDS), thinking that glycols can cause liver and kidney damage and act as a skin irritant. Considering that over 4000 beauty products in the U.S. alone contain propylene glycol, this was a big deal, to say the least. However, MSDS sheets refer to 100% concentrations of a substance. In the small concentrations used in skin care cosmetics, glycols are not a concern. According to the U.S. Department of Health and Human Services, propylene glycol is classified as GRAS (Generally Recognized As Safe), and proclaims, “Studies have not shown these chemicals [propylene or the other glycols as used in cosmetics] to be carcinogens”. [Read more: Is Propylene Glycol Safe in Beauty Products?]

3.) You want to wear a mask for at least 20 minutes for best effects, unless it contains an AHA.

In general, you want to wear a mask for at least 20 minutes. The reason? After a certain amount of time, ingredients will reach a threshold of penetration in the skin, meaning that very little is to be gained from having the material on the skin longer (Advanced Drug Delivery Reviews, 2002).

While some ingredients in certain delivery systems will take very little time to reach the deeper layers of the skin, most will take somewhere between 5-60 minutes to dissolve or absorb into the skin. Water and volatile compounds take 5-10 minutes (Textbook of Cosmetic Dermatology, 2010). The rate of dissolvation or absorption of the other ingredients depends on the environmental conditions (especially humidity), the temperature of the skin itself, the size of the ingredients, and the amount of product applied (Textbook of Cosmetic Dermatology, 2010). It’s a safe bet to say that, after 20 minutes, you’re getting about 80% of the effects of any mask, and after 60 minutes, you’re getting about 99%.

One word of caution: You do not want to leave a mask with AHAs on for longer than recommended. AHAs, like glycolic, lactic, and malic acids, generally are formulated with water-soluble components that will dissolve first. This means that the AHA becomes more and more concentrated, the longer it rests on your skin.

So it is important to always follow the instructions on the label. Otherwise, you can do more harm than good. For best results, look for masks that are designed to be applied for longer periods of time.

What are the Best Sheet Masks?

My favorite sheet mask is Bel Mondo Beauty Anti-Aging Facial Sheet Mask ($45.00 for four, Belmondobeauty.com). First of all, this mask is made of biocellulose, so it binds tightly to the skin, without getting any air pockets and missing portions of your skin. It also enables you to walk around and go about your business while wearing it. Secondly, the Bel Mondo Beauty Anti-Aging Facial Sheet Mask has a superior assortment of ingredients to other masks I’ve tried, including hydrating sodium hyaluronate and olive oil, skin-firming Skinasensyl, palmitoyl tri-peptide and palmitoyl hexapepide, skin-refining Syn-Tacks, and antioxidant vitamin E. It makes a profound difference in your skin every time you use it! I definitely recommend it as a special spa-like treatment for the skin; I love using mine in the bath after a long day!

Purified water, glycerin, sodium hyaluronate, propylene glycol, sodium alginate, soluble collagen, chlorphenesin, Skinasensyl (acetyl tetrapeptide-15, sodium citrate), Syn-Tacks (palmitoyl dipeptide-5, palmitoyl dipeptide-6), Citrustem (orange stem cells), olive oil, tocopherol, palmitoyl tripeptide, palmitoyl hexapeptide, biosol, retinyl palmitate, alpha lipoic acid, fragrance