A moisturizer, or emollient, is a cosmetic preparation used for protecting, moisturizing, and lubricating the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...

. These functions are normally performed by sebum produced by healthy skin. The word "emollient" is derived from the Latin verb ''mollire'', to soften.

Mechanism of action

In the human body, water constantly evaporates from the deeper layers of the skin through an effect known as

transepidermal water loss image:Tewameter Principle.png, Principle of an instrument measuring transepidermal water loss. Water vapor is diffusing through the transparently shown cylinder. The yellow arrow symbolizes the diffusion direction. The two dark red square elements ...

(TEWL). By regulating its water content, human skin naturally maintains a dry, easily shed surface as a

barrier A barrier or barricade is a physical structure which blocks or impedes something. Barrier may also refer to: Places * Barrier, Kentucky, a community in the United States * Barrier, Voerendaal, a place in the municipality of Voerendaal, Netherl ...

against pathogens, dirt, or damage, while protecting itself from drying out and becoming brittle and rigid. The ability to retain moisture depends on the

lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many vir ...

between the

corneocytes Corneocytes are terminally differentiated keratinocytes and compose most of the stratum corneum, the outermost layer of the epidermis. They are regularly replaced through desquamation and renewal from lower epidermal layers and are essential for ...

. Moisturizers modify the rate of water loss, with active ingredients of moisturizers falling into one of two categories: occlusives and humectants. Occlusives form a coating on the surface of the skin, keeping moisture from escaping. The more occlusive the formulation, the greater the effect. Ointments are more occlusive than aqueous creams, which are more occlusive than

lotion Lotion is a low-viscosity topical preparation intended for application to the skin. By contrast, creams and gels have higher viscosity, typically due to lower water content. Lotions are applied to external skin with bare hands, a brush, a clean ...

. Water loss through the skin is normally about 4–8 g/(m²⋅h). A layer of

petrolatum Petroleum jelly, petrolatum, white petrolatum, soft paraffin, or multi-hydrocarbon, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons (with carbon numbers mainly higher than 25), originally promoted as a topical ointment for its he ...

applied to normal skin can reduce that loss by 50–75% for several hours. Oils naturally produced by the human body moisturize through this same mechanism. Humectants absorb water. They can absorb this water from the air and moisturize the skin when the humidity is greater than 70%, but more commonly they draw water from the dermis into the epidermis, making skin dryer. A study published in Skin Research and Technology in 2001 found no link between humectants and moisturizing effect. When used in practical applications, they are almost always combined with occlusives. Moisturizers often contain water, which acts as a temporary hydration agent as well as a way for the absorption of some components and evaporation of the moisturizer.

Kinds

There are many different types of moisturizers.

Petrolatum Petroleum jelly, petrolatum, white petrolatum, soft paraffin, or multi-hydrocarbon, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons (with carbon numbers mainly higher than 25), originally promoted as a topical ointment for its he ...

is one of the most effective moisturizers, although it can be unpopular due to its oily consistency. Other popular moisturizers are cetyl alcohol, cetearyl alcohol, cocoa butter, isopropyl myristate, isopropyl palmitate, lanolin, liquid paraffin, polyethylene glycols, shea butter, silicone oils, stearic acid, stearyl alcohol and

castor oil Castor oil is a vegetable oil pressed from castor beans. It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its density is 0.961 g/cm3. It includes a mixture of triglycerides in which about ...

, as well as other oils. Moisturizers may also be available as

cream Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process ...

s, ointments, bath oils, or soap substitutes. Mineral oils and waxes are insensitive to

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

or rancidity. For this reason, they have essentially replaced

vegetable oil Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or f ...

s in emollients and topical medication. Moisturizer cosmetics may additionally contain antioxidants,

ceramide Ceramides are a family of waxy lipid molecules. A ceramide is composed of N-acetyl sphingosine and a fatty acid. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells, since they are component lipids that make ...

s, emulsifiers,

fragrance An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently ...

s, penetration enhancers, preservatives, and

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

s. Some products are marketed as having anti-wrinkle and skin enhancement effects. Many plant and animal extracts have been claimed to impart skin benefits, with little scientific evidence.

Use

Moisturizers are used for the treatment of certain skin diseases, such as

psoriasis Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by raised areas of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete ...

, ichthyosis vulgaris,

xerosis Xeroderma, xerosis or xerosis cutis, or simply dry skin, is a skin condition characterized by excessively dry skin. The medical term ''xeroderma'', meaning "dry skin", derives from modern Latin, ''xero-'' 'dry' + Greek ''derma'' 'skin'. In most ...

, and

pruritus Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasant ...

in atopic dermatitis. More often, they are bases or vehicles for

topical medication A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...

, such as in Whitfield's ointment. They are often combined with humectants, such as salicylic acid and

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...

. Moisturizers are also widely used in sunscreens,

antiperspirant A deodorant is a substance applied to the body to prevent or mask body odor due to bacterial breakdown of perspiration or vaginal secretions, for example in the armpits, groin, or feet. A subclass of deodorants, called antiperspirants, preven ...

s, skin cleansers,

shaving cream Shaving cream or shave cream is a category of cream cosmetics used for shaving preparation. The purpose of shaving cream is to soften the hair by providing lubrication. Different types of shaving creams include aerosol shaving cream (also kn ...

s, aftershaves, and

hair tonic Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fin ...

s. Moisturizers are used in disposable napkins to prevent dry skin and napkin dermatitis. A

Cochrane review Cochrane (previously known as the Cochrane Collaboration) is a British international charitable organisation formed to organise medical research findings to facilitate evidence-based choices about health interventions involving health profes ...

noted that moisturizers show some beneficial effects in eczema. The same review did not find evidence that one moisturizer is better than another.

Potential health risks

Over-moisturization

Persistent moisturization to the skin from exposure to water may contribute to an allergic reaction or irritant contact dermatitis, and can result in penetration of foreign objects. Changes in the skin's normal ecological environment, in or on the skin, can also support the overgrowth of pathological organisms.

Allergens

Moisturizers containing some aromas or food additives may trigger an immune reaction or even cause users to develop new allergies. There is currently no regulation over use of the term "hypoallergenic", and even pediatric skin products with the label were found to still contain allergens. Those with eczema are especially vulnerable to an allergic reaction with lotions and creams, as their compromised skin barrier allows preservatives to bind with and activate immune cells. The

American Academy of Allergy, Asthma, and Immunology Founded in 1943, the American Academy of Allergy, Asthma & Immunology (AAAAI) is a professional medical membership organization of nearly 6,800 allergist/ immunologists and related professionals around the world with advanced training and experie ...

released a warning in 2014 that natural lotion containing ingredients commonly found in food (such as goats milk, cow's milk, coconut milk, or oil) may introduce new allergies, and an allergic reaction when those foods are later consumed. A paper published in 2021 by researchers at St. George’s, University of London found that frequent skin moisturization in early life might promote the development of food allergy, even when skin conditions such as eczema are taken into account.

Fire risk

Paraffin based skincare products and contaminated clothing can pose a serious fire hazard. Between 2010 and 2018, paraffin was linked to 50 fire incidents (49 of which were fatal) in the U.K. A West Yorkshire Fire and Rescue Service study found that clothing contaminated with cream containing only 21% paraffin, when set alight, was fully engulfed in flame in 3 seconds. The Medicines and Healthcare products Regulatory Agency (MHRA) released a warning in 2008 about the flammability of paraffin-based products. MHRA recommends that sheets of people using paraffin are changed regularly, and that people refrain from smoking or bringing open flames around patients using paraffin. MHRA also recommends that skin creams containing any paraffin have a flammability warning on the packaging.

Brands of moisturizers

* Artistry * Aveeno * Bath & Body Works * CeraVe * Cetaphil *Curel * Dial * Eucerin * Gold Bond *

Garnier Garnier () is a mass market cosmetics brand of French cosmetics company L'Oréal. It produces hair care and skin care products. Launch ''Laboratoires Garnier'' was founded in France in 1904 by Alfred Amour Garnier. The company's first product ...

* Jergens * Johnson & Johnson * Lux * Neutrogena *

Nivea Nivea (, stylized as NIVEA) is a German personal care brand that specializes in skin and body care. It is owned by the Hamburg-based company Beiersdorf Global AG. The company was founded on 28 March 1882, by Paul Carl Beiersdorf. In 1890, it w ...

* Olay * Sebamed * Sensavor * Simple Skincare * Suave *

Vaseline Vaseline ()Also pronounced with the main stress on the last syllable . is an American brand of petroleum jelly-based products owned by transnational company Unilever. Products include plain petroleum jelly and a selection of skin creams, soa ...

References

{{cosmetics Skin care Emollients and protectives