I am sure you will be shocked when you read any articles or blogs on how cosmetic ingredients can get absorbed into your skin. Up to 100% of cosmetic ingredients or to add fuel to fire, many will use the word "Chemicals", will get absorbed into your skin. The scientific chemical name for the most common chemicals that we come in contact everyday are as follows:
• Water - Dihydrogen monoxide
• Air we breathe comprises of Oxygen, Carbon dioxide, Nitrogen, etc.
• Salt - Sodium chloride
• Sugar - Sucrose
And so many more and I'm sure you get the idea. So a little less fear mongering about chemicals and more about facts.
How ingredients permeate into the skin really depends on many factors. Our skin is a barrier and that itself already has an impact how ingredients 'travel' into the skin. Let's take a look at how the skin looks like.
The skin, your skin, my skin, is made up of three layers. Epidermis being the top most where you can see and come in contact with skincare products, bacteria, allergens, etc. This layer is made up of sebaceous lipids and epidermal lipids that contain triglycerides, wax esters, squalene, mixture of ceramides, free fatty acids and cholesterol. The epidermis acts as a barrier to protect our body from getting viral or bacteria infection. It regularly sheds dead skin cells called Keratinocytes and reveal new cells. It contains melanin that protect the skin from UV damage.
The dermis is the middle portion where you can find all the blood and lymph vessels, nerves, hair follicles and sweat glands.
The last layer is called the Subcutaneous tissue or Hypodermis which compromises mostly of fats (decreases as age goes up) and acts as an insulation and cushioning to prevent injuries to our muscles.
Most cosmetics or skincare are meant to beautify or improve the skin barrier and hence the ingredients usually stays on top of the skin, I repeat usually. The top most layer i.e. Epidermis looks like cement blocks or bricks that are stacked together. Imagine a product that has been applied to the skin and the ingredients will have to make it's way in to perform it's function to moisturise, hydrate, soothe, calm, reduce inflammation, etc. How much of these ingredients get absorbed into the skin is what most of us are interested in and are based on these few factors:
• molecular size of the ingredients
• integrity of the skin
• location of the skin where ingredients come in contact
• age of the skin
• contact time of ingredients on the skin
I understand most people, even myself are not equipped with a scientific background but I will use my graphic visualisation skills to explain it as much as I can in layman terms .
The bigger the molecular size of the ingredients, the harder it is for them to get penetrated into the deeper layers of the skin. It has to 'fight' through the 'brick layers' and may get stopped there as it's too big to travel further. So if you smear pizza on your skin, do you think it will get absorbed? I'm sure you know the answer. The top layer, Epidermis, has an affinity with oils since it is made up of lipids. Have you also noticed that when you wash yourself, your skin repels water instead of absorbing it? Can you imagine what will happen to us if our skin absorbs 100% of what is put on top of it when we take our daily twice or thrice daily showers?!
Most ingredients such as oils, butters, Hyaluronic acid, humectants get absorbed into the epidermis layer but not penetrated further because of the big molecular sizes. Waxes do not get absorbed at all and stays on top of the skin acting as an occlusive barrier to prevent water loss.
There are ingredients that do penetrate deep into the layers of the skin and to the blood stream, and they usually have smaller molecular sizes. They are able to 'wriggle' their way pass the 'brick walls' of the epidermis and into the dermis where eventually it can end up in the blood stream. Essential oils are such ingredients that have smaller molecular sizes and are very potent too. Hence they are to be used with safety in mind (safety dermal limits according to Cosmetic Products Safety Assessor and International Fragrance Association, IFRA).
Younger skin such as babies, children, young people will react well to topical applications from skincare far better than adults and older people (age factor). The skin on our buttocks and feet are much thicker as compared to our face. Therefore the skin on our face and body is able to absorb cosmetic ingredients better than our buttocks and feet (location of the skin). Someone who has sensitive skin or problematic skin usually have compromised skin barrier (skin is not functioning normally). That can lead them to experience greater sensation when products are applied onto their skin. It is also the reason why sensitive skin reacts easily to cosmetics or skincare (integrity of the skin).
The duration of contact from cosmetic ingredients can also determine how much it gets absorbed into the skin (contact time). Let's say you mist your face with spring water, the water will not be absorbed into the epidermis (remember the epidermis is a barrier and repels water). Water evaporates. What you are essentially doing is to freshen your skin with the spring water, that's all. When you apply a facial moisturiser or a facial oil, the product will include some type of oils, butters, waxes, humectants that will stay on your skin for a certain amount of time. During this duration, some of the ingredients will get absorbed into the epidermis and some into the blood stream (those with smaller molecular sizes).
I hope I have made it a bit easier for you to understand better that how ingredients are absorbed into the skin and it all depends on the factors that I have listed above.
For more readings on Anatomy and Physiology of the skin:
• https://opentextbc.ca/anatomyandphysiology/chapter/5-1-layers-of-the-skin/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2835894/
