Within the skincare community, you may hear some terms casually thrown around such as moisturizer, humectant, emollient — as if these (somewhat) complex words were apart of everyone’s vernacular. Moisturizer, maybe. But humectant, emollient, and occlusive agents? Not so much.
In short, humectants, emollients, and occlusive agents are integral parts of a moisturizer. However, the lines between these categories are murky as some ingredients can be apart of multiple categories. Below I have outlined each category’s main purpose and some examples to help further understanding.
Humectants are chemicals that are able to hold many times their weight in water depending upon the chemical (hyaluronic acid for example can hold up to 1000x its weight in water!). When placed onto damp skin, the skin is continuously moisturized by the water from the surrounding environment held onto by the chemical. However, if the surrounding environment does not contain much water, these chemicals can be rather drying and irritating to the skin (this is why it is suggested to have a slightly damp face when you apply something like hyaluronic acid). These ingredients can be both from synthetic and natural origin. Examples of humectants include: hyaluronic acid, propylene glycol, polyethylene glycol (PEG), glycerin, lactic acid, and honey.
Occlusive Agents Think of this as an ingredient to physically “lock-in” all that precious, so easily lost moisture, such as waxes, oils, and petroleum. Usually, occlusive agents on their own can be a bit thick and annoying on the skin, so they are used in combination with other (non-occlusive) emollients to lessen the discomfort. These ingredients are things I personally like to use in rather severe winter conditions or at bedtime for intense hydration.
Emollients aid in a moisturizer’s spreadability on the skin. Further, emollients can form occlusive layer barriers (via occlusive agents) to the skin to the outside world. Primarily, emollients keep dry, rough, and flaky skin smooth and even-textured. Think of this as a soothing and moisturizing protectant against the outside world, or fairly roughly speaking, it’s as if the properties of a humectant and an occlusive agent were to be combined together. Moisturizers with high emollient properties are usually prescribed for people with psoriasis or eczema because these ingredients have a two pronged attack: they treat the irritating dryness and the underlying issue: a damaged moisture barrier. Examples include lanolin, petroleum, mineral oil, shea butter, squalene, beeswax and paraffin.
From there, the combination of these three fabulous categories are what make up your everyday (non-medicated) moisturizers! Keeping in mind, changing the ratios between each category and the level to which your moisture barrier is damaged are why certain moisturizers may work fabulously for you and cause breakouts for someone else.