The outermost layer of skin (the epidermis) forms a protective barrier for our bodies, binding in moisture and keeping foreign bodies out (including bacteria, microorganisms and other pathogens). For skin to remain healthy and vibrant, it is important to maintain an adequate level of moisture. In addition to staying hydrated by drinking water, skin moisture is affected by humidity, wind, exposure to hot water, soap, and other environmental factors. Moisture is constantly lost from the skin – effective moisturizers should help replace this lost moisture and reinforce the skin’s barrier to help protect skin from further dehydration.
The skin consists of three primary layers: the epidermis, the outermost layer; the dermis or middle layer; and the hypodermis, the innermost layer. When water passes from the dermis through the epidermis and evaporates from the skin’s surface, this is known as transepidermal water loss (TeWL). The main function of a moisturizer is essentially to reduce TeWL by attracting water to the skin and/or increasing water retention by reinforcing the skin’s natural barrier function.
Moisturizers Mimic the Barrier Function
Skin moisturizers are, in essence, some combination of water and fats or other lipids. Moisturizers can be classified by their oil content, with ointments and balms that contain no water on one side and emulsions, a mixture of oil and water combined with an emulsifying agent (think of the role of egg when making mayonnaise) on the other. There is a broad range of options when it comes to moisturizers within and across categories.
Natural Oils: Natural oils are used extensively throughout the world as moisturizers but in spite of their growing popularity, there is surprisingly limited data on their efficacy and safety profile. it seems that the ratio of oleic acid (OA) to linoleic acid (LA) in natural oils determines their effect on the skin. Positive effects for very dry and sensitive skin are generally associated with low OA and high LA ratios. High LA concentrations have been shown to accelerate skin barrier development and repair, hydrate the skin, and, as a result, reduce the severity of atopic dermatitis and be steroid sparing. Some natural oils with the highest LA/OA ratios are safflower oil, sunflower seed oil, and sea buckthorn seed oil. In contrast, olive oil, with its relatively low LA/OA ratio, can damage the skin barrier.
Ointments: These preparations are predominantly fats or oils, with little or no water. These tend to have excellent occlusive properties and generally do not sting or burn. Occlusives mimic the skin’s barrier function; with their high oil content, they physically block water loss and pathogens, protecting skin from foreign agents. For this reason, occlusive products can be very effective in the treatment of sensitive skin conditions such as eczema. While occlusives can be effective at trapping moisture that already exists within the skin, they do not draw moisture to the skin. Occlusive also have the potential to clog pores and may be perceived as greasy or sticky.
Balms: Balms are formulated to leverage the benefits of an ointment, but improve upon the sensory experience of the product; they go on more smoothly and are intended to have a silky instead of greasy feel (this subjective quality of a product is called “skinfeel”). Balms might contain waxes or other ingredients that soften when exposed to warmth, so they melt into the skin.
Cream: Creams follow ointments and balms in the amount of oil they contain and are also very good at sealing in moisture. Moisturizing creams are predominantly oil-based with some water (often called water-in-oil emulsions). Creams are typically less greasy and are formulated with many different types of ingredients to achieve specific results. Two of the most essential types of ingredients used in moisturizing creams are emollients and humectants:
- Emollients, preparations designed to soften the skin, refer to the oils and fats we’ve talked about so far, they include fatty acids, cholesterol and ceramides. When skin is moist, the cells are plump with water but when that moisture is drawn out by dry air, the cells can shrink, the edges can curl, leaving small cracks or space between them and skin can appear rough and flakey. Emollients in a moisturizing cream can fill the space between them, acting to smooth these dry, flakey skin cells and giving the appearance of smooth, hydrated skin.
- Humectants are also widely used in moisturizing creams. These are hygroscopic (water-attracting) substances that attract water from the air into the stratum corneum, the outermost layer of skin. One very commonly used humectant ingredient is glycerin.
- Functional ingredients for sensitive skin: in addition to those mentioned above, there are a number of specific ingredients that have been shown to soothe and calm irritated skin. Some of the functional ingredients we use widely in our products include hemp oil, hemp seed oil, bisabolol, sunflower and safflower seed oils, seabuckthorn seed oil, colloidal oatmeal and sea whip extract.
Lotion: Of the products discussed here, these contain the least amount of oil. Because lotions are predominantly water with some oil (oil-in-water), they evaporate quickly and typically lack the occlusive properties of ointments, balms and creams. It has been found that these types of products actually add very little water to the skin.¹ Lotions are typically emollients in water with a preservative or alcohol and rarely contain functional ingredients. Lotions are often not recommended for those with sensitive skin as they are the most likely to sting cracked or broken skin.
How to moisturize
Ideally, someone with sensitive skin will moisturize every time their skin is in contact with water and frequently throughout the day whenever skin feels dry. It may be tempting to skip the process, but for those with extremely sensitive skin and conditions like eczema, proper moisturization is the first line of defense against exposure to pathogens and allergens that fuel the itch scratch cycle.
When Moisturizing: apply a thick layer of moisturizer all over your skin within three minutes of bathing or showering to “lock in” moisture and protect the skin barrier. Rather than drying fully with a towel, gently “pat dry” leaving skin moist before you moisturize. If you use a prescription topical medication, apply it as directed, before you apply moisturizer. Use a moisturizer specifically formulated for sensitive skin that omits known irritants and allergens (like lanolin, dye, fragrance, harsh preservatives). If you have very sensitive skin, it’s important to keep your products free of contaminants and pathogens. Opt for products that come in a tube or airless delivery method or use a clean implement like a spoon or rather than your hands to remove moisturizer from the container.
Your hands and face are typically the most exposed part of your body, so treat them with special care. Moisturize your hands every time you wash them or when they come into contact with water. Carry a small tube of moisturizing cream with you to apply whenever they start to feel dry. Protect sensitive skin from exposure to cold, dry air and hot water.