Where Does Skincare Go After You Apply It?
Do your pores really “drink up” products? Does retinol pump through our veins? Cosmetic chemists and dermatologists weigh in.
If you're like us, you won't be putting down your favorite products anytime soon because there's joy and relaxation in your a.m. and p.m. skincare applications. It's a welcomed ritual that helps start and close your day, but beyond the sensorial benefits, we can't help wondering what's happening during each slather and mist. From eye cream to SPF, every product plays a crucial part in achieving our skincare goals, but what actually happens to our favorite formulas once applied?
You may have seen stats that claim 60 percent of all skincare absorbs into your bloodstream—and only takes 26 seconds to get there. However, these are just a couple of the oft-cited stats that have recently gained popularity, despite not being scientifically backed.
To finally set the record straight and eliminate misinformation, we turned to cosmetic chemists, dermatologists, and skincare experts. Keep reading for their insights into how the skin functions, and what really happens once skincare products are applied.
How does the skin function?
To understand what happens to our skincare once applied, we need to know how the skin works first. Skin is our largest multifunctional organ and operates as our "protective barrier against harmful foreign substances in the environment," says Kristina Kitsos, RN, a cosmetic nurse in Beverly Hills, Calif.
The skin is made up of three layers: at the top we have the epidermis, known as the waterproof barrier. It's also important to note that within the epidermis is the stratum corneum, which is made up of "dead skin cells arranged like tiles on a roof, overlapping one another and glued together with fatty acids," says Kitsos. The dermis is the middle layer of the skin and where elastin, collagen, connective tissue, blood vessels, hair follicles, and sweat glands reside. And finally, the bottom layer of the skin is called the hypodermis, the innermost layer of the skin that comprises fat and connective tissue.
How does the skin absorb skincare products?
When talking about skincare products, it's important to note that skin is not a sponge. "Most topical skincare products work on the skin's surface," says Ron Robinson, cosmetic chemist at BeautyStat.com. "Most products don't even make it to the dermis, which contains the blood supply."
If you're wondering why your skincare feels like it's absorbing (I did, too), that sinking-in sensation you feel after applying skincare is really just air-drying in action. According to derms, the majority of ingredients start evaporating into thin air as soon as they're applied.
While "absorption" means that something has made its way into the bloodstream, skincare "penetration" means an ingredient has made its way through the stratum corneum into the deeper layers of the skin. "When it comes to skincare, penetration is the goal so that the active ingredients can work to hydrate and fortify the skin while remaining in the targeted skin layer for maximum efficacy," says Kitsos.
However, this gets tricky because of your stratum corneum. The shield of fatty acids, sebum, and ceramides is also water-repellent, which is why you can take a bath without turning into a water balloon. The problem is that skincare consists of a lot of water because it's the most effective way to dissolve and dilute active ingredients.
Enter penetration enhancers, which are ingredients like certain alcohols or fatty acids (such as linoleic and oleic acid) that enhance the chances of another ingredient's penetrability. Think of it like bringing a friend to a party where they're not invited. "These ingredients penetrate the skin and decrease the skin's innate barrier resistance. In doing so, they allow other ingredients to enter along with them," says Kisos. "Penetration enhancers are frequently used in transdermal medications, but they have also become widespread in cosmetics and skincare products."
There are other factors that can impact this penetrative process as well. With serums, they're "very liquidy and can easily penetrate the skin delivering the ingredient efficiently, compared to thick creams or moisturizers," explains Shuting Hu, PhD, a cosmetic chemist and founder of Acaderma. "On the other hand, creams will sit on top of the epidermis for longer as they likely include an occlusive ingredient, like petrolatum or waxes."
Molecular size also factors in. Ingredients such as vitamin C, vitamin E, and hyaluronic acid can easily penetrate the epidermis since they have smaller molecular structures. But some ingredients have larger molecular structures, which means they can't penetrate the skin and will end up sitting on the surface of the skin," says Dr. Hu. A common example is oils, silicones, and wax-based elixirs. That's not to say that these non-penetrative ingredients aren't beneficial—they can seal the skin and give a hydrating effect, improving your outer skin texture.
Here's where things get a bit dicey. There are some beauty ingredients that manage to infiltrate both the circulatory and lymphatic systems. To achieve this feat, molecules need to be ultra-small, and have both hydrophilic (water) and hydrophobic (oil) components that increase their solubility, says Dr. Sheilagh Maguiness, MD, board-certified dermatologist and co-founder of Stryke Club. Retinol is an example of a bloodstream-entering ingredient (it's listed on California's Prop 65 for potential "reproductive toxicity" for this reason), which is why pregnant women should avoid using it entirely.
Certain ingredients in chemical sunscreens, such as avobenzone and oxybenzone, have also been found to absorb directly into the bloodstream—as well as chemical molecules like parabens and phthalates that mimic hormones and are distributed throughout the body. The effect of chronic chemical exposure from cosmetics on long-term health isn't very clear, but it's definitely an argument for the importance of clean beauty.
Does skin thickness matter?
Yes, location matters, too. The thickness of the skin varies on our bodies, which impacts ingredient or product permeability. "In general, the thinner the skin, the more potential for penetration there is," says Dr. Maguiness.
Some thinner areas are the eyelids, areas containing hair follicles or sweat glands, and some thicker areas are the soles of your feet or palms of your hands. It's important to note that people who suffer from "skin conditions like atopic dermatitis have an increased chance of products actually getting into their bloodstream because the integrity of their skin barrier is compromised," says Dr. Maguiness.
So, can products actually get into our bloodstream?
The truth is yes and no. "Studies have shown that some of these tiny skincare chemical molecules, especially ones found in sunscreen, show up in some people's bloodstreams," explains Kitsos. But even so, this doesn't justify the fear-mongering and misinformation that surrounds the dangers of daily skincare application. It would take "incredibly high doses and years of consistent administration for the most intense ingredients to enter the bloodstream through the skin, says Dr. Hu.
In other words, you can rest assured knowing your favorite skincare products are very unlikely to ever get into your bloodstream—your epidermis and dermis layers are great at doing their jobs.