Myth Busting: Dermal Absorption of Skincare Ingredients

Sorry, but your skin doesn't absorb products. 

At least not in the way that people use to scare you into buying their stuff.

If you follow our blog, you know bareLUXE is a green and clean beauty brand that stands against toxic marketing practices. Natural, clean, minimal-ingredient skincare products can co-exist with complex, synthetic products without trying to use fear to drive sales.

Let's look at the science of dermal absorption and discuss what exactly happens to your skincare products once they leave the tube and arrive on your face.

Dermal Absorption of Cosmetics

When it comes to fear-based skincare marketing, using examples of things that sound scary is a tactic to legitimize the argument.

Of course, toxic and occupational dermal exposures are real concerns. However, comparing whole-body pesticide contamination exposure in a farm worker to using non-organic (and thus potentially pesticide-containing) skincare products is just ridiculous.

It's also important to note that dermal absorption, or the use of the skin as a delivery system for drugs, is a well-established practice in the medical field. However, the science behind something like a transdermal drug patch has a lot to it. It's not just a simple matter of putting some nicotine on a bandaid and having it enter the bloodstream.

Absorption vs Penetration

Absorption refers to the process by which a substance is taken up by the skin and enters the bloodstream; penetration refers to the ability of a substance to reach the deeper layers of the skin without entering the bloodstream.

The vast majority of cosmetic ingredients do not absorb into the bloodstream and instead work on the skin's surface to improve its appearance. This can include moisturizing the skin, reducing the appearance of fine lines and wrinkles, evening out skin tone, and more. 

Cosmetic products are formulated to penetrate the epidermis - that's where we want them. Some, like sunscreens, are formulated to sit on top and not penetrate. 

The outer stratum corneum acts as a barrier, but getting below it allows your active ingredients to do their job. While the fear is that potentially harmful substances will accumulate in your body, skin care products are rarely a concern.

One exception is hydroquinone. Studies have shown that hydroquinone can be absorbed through the skin up to 45% of what is applied, but it is not clear how it is metabolized in the body. Arguably, that does sound scary, but the total dose absorbed would be very low overall. However, this is why it's so important to follow the advice of a qualified dermatologist if you're using any prescription medical treatments to lighten or treat your skin.

Microplastics are something that we are very concerned about because the do accumulate in tissues, but generally not from being absorbed through topical use. They enter your body when you consume them through lip-licking, eating, drinking, and breathing them in. 

Skin Barrier

The skin is an effective and protective barrier, primarily due to its waterproof nature. Getting chemicals past the brick-and-mortar structure and into the deeper layers can be tricky. Ingredients that can penetrate are able to exert their actions within the dermis.

In fact, having a compromised skin barrier is one of the reasons people are more likely to develop allergic reactions to products (more irritants are able to pass through). 

Several factors can affect how well a skincare ingredient is able to penetrate the skin barrier:

• Molecular size and molecular weight: Smaller molecules can generally penetrate the skin more readily than larger ones. The differences between collagen and hyaluronic acid are great examples. Some peptides can penetrate, but large proteins cannot.
• Solubility and polarity: Ingredients soluble in oil are generally able to penetrate the skin more easily than water-soluble ones. This is where waterless products can have an advantage. 
• pH: Products with a pH similar to that of the skin (around 5.5) penetrate well.
• The condition of the skin: The health and condition of the skin can also affect its ability to absorb products. For example, damaged or inflamed skin may be more permeable, while healthy skin may be more resistant to penetration. Thick skin with extra dead skin cells is also harder to penetrate.
• The presence of other ingredients: Certain ingredients can either enhance or inhibit penetration. For example, surfactants (such as sodium lauryl sulphate) can help to improve the penetration of other ingredients, while occlusive agents (such as petroleum jelly) can create a barrier that inhibits penetration. Some common penetration enhancers are DMI (dimethyl isosorbide), alcohols, and enzymes.

Fast vs Slow Absorption

The sensorial aspects often describe cosmetic products. How do they feel on the skin? How long do they feel like they're there? Are they sticky or powdery? Are they light or heavy?

Some of what you experience with skincare, particularly with water-based products, is actually evaporation. How quickly it disappears can actually have nothing to do with absorption or penetration at all. Something that is really light and seems to disappear immediately likely evaporated. What's left behind may be the after-feel related to the actual ingredients that were deposited on the skin.

5 Ways to Maximize Active Ingredient Activity

In order to maximize penetration so that your active ingredients can work within your skin rather than just sitting on top, the following principles are helpful:

• Start with clean skin that is slightly moist (water is a penetration enhancer)
• Use exfoliants regularly but not excessively (removing dead cells improves penetration but overdoing it will damage your barrier)
• Opt for oil-based active ingredients and oil serums when the option exists. Tetrahexyldecyl ascorbate is a great example.
• Consider microneedling with a properly trained provider if you have a specific active you're hoping to deliver
• Apply occlusives last after any active ingredients

Alkilani AZ, McCrudden MT, Donnelly RF, Transdermal drug delivery: innovative pharmaceutical developments based on disruption of the barrier properties of the stratum corneum (open access), Pharmaceutics 2015, 7, 438-70.

FDA, Guidance for industry: residual drug in transdermal and related drug delivery systems, 2011.

Bronaugh RL & Maibach HI, Percutaneous Absorption: Drugs – Cosmetics – Mechanisms – Methodology (3rd Edition); CRC Press: 28 May 1999.

Pastore MN et al., Transdermal patches: history, development and pharmacology (open access), Br J Pharmacol 2015, 172, 2179-209.

Byel Kim, Hang-Eui Cho, Sun He Moon, Hyun-Jung Ahn, Seunghee Bae, Hyun-Dae Cho & Sungkwan An. Transdermal delivery systems in cosmetics. Biomedical Dermatology. volume 4, Article number: 10 (2020) 

Tampucci, Silvia, Susi Burgalassi, Patrizia Chetoni, and Daniela Monti. 2018. "Cutaneous Permeation and Penetration of Sunscreens: Formulation Strategies and In Vitro Methods" Cosmetics 5, no. 1: 1

Lim, S.H., Sun, Y., Thiruvallur Madanagopal, T. et al. Enhanced Skin Permeation of Anti-wrinkle Peptides via Molecular Modification. Sci Rep 8, 1596 (2018).