Beauty Science: How do Moisturisers Work?

I don’t know about you, but it really bugs me when I don’t understand how things that I do on a daily basis work.  Take moisturisers.  This is a product that I use on a daily basis, but didn’t really know how it works.  Obviously it does something that keeps moisture in my skin, but I figured it was more complicated than transferring water through my skin, after all, I am not more moisturised after a bath.

First question that needs to be addressed is how does skin get dry? The process is technically called Transepidermal Water Loss, or (TEWL), and refers to the process of water passing through our skin to the atmosphere.  Our skin acts as a barrier to the atmosphere, but when our skin is unhealthy, or it is really dry, too much moisture may escape.  Things like cuts, scratches, or burns that damage our skin can stop it from providing that barrier and doing its job.  Similarly, if your skin becomes too dry, it can disrupt the moisture barrier. When your outer layer of skin, or corneocytes, get too dry, the proteins that bind them together can breakdown causing your skin to look scaly and flake off, which also disrupts the skins ability to hold in moisture.

So what can you do?  There are three types of moisturisers: Occlusives, Emollients, and Humectants.


Occlude means to close or stop. Similarly, these types of moisturisers create a barrier on your skin that stops you from loosing moisture from your skin. They tend to feel greasy on the skin, because it is a thin greasy layer that locks in the moisture. Therefore, these types of moisturisers are better for your body than your face because your body has less oil glands than your face.  They can also irritate the skin and block pores creating breakouts. Occlusives include: petroleum jelly, cocoa butter, and beeswax to name a few. I personally do not like the feel of these moisturisers and limit their use to my lips. However, they work well for preventing moisture loss, and I know many people who love cocoa butter moisturisers.


If you already notice that your skin looks dry and flaky, then an emollient would be a good choice. Emollients work by filling in the gap that are created when the protein between  your corneocytes break down. After using an emollient based moisturiser, your skin will feel softer and look less scaly. Emollients can be made from many ingredients including: vegetable waxes, like palm or coconunt; oils, like castor oil; or silicones. However, the effectiveness of emollients differs from person to person, so it might take some trial and error to find the best one for your skin. They also have to be re-applied often.


Humectants are ingredients that attract water. They pull up moisture from deeper layers of skin, and, if it is humid enough, can pull moisture out of the air. If your skin is very dry, humectants can be problematic because although they will attact more moisture from deeper levels of skin, they do not replace that moisture, so they can make you skin overall drier. Some natural humectants include: hyaluranic acid, aloe, alpha hydroxy acid, and honey.

Each type of moisturiser has strengths and weaknesses, so most moisturisers will contain a mix of the above types. So it will be a matter of testing products until you find the one that works for you.  Is there a moisturiser that you recommend? Please let me know below. Maybe it will help someone else find something that works well for them with less trial and error.

As always, if you notice any errors in this post, please contact me so I can correct the error.