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Moisturizer

life science Maturity 11-13 Next article →

A moisturizer, also known as an emollient, is a cosmetic preparation. Its primary purposes are to protect, moisturize, and lubricate the human skin. Healthy skin naturally produces a substance called sebum to perform these functions. The term emollient comes from the Latin verb *mollire*, which means to soften.

By using these products, people can help maintain the skin's barrier. This barrier is vital for protecting the body against pathogens, dirt, and physical damage.

To understand how moisturizers work, we must look at how skin loses water. In the human body, water constantly evaporates from the deeper skin layers. This process is known as transepidermal water loss. Normally, skin loses about 4 to 8 grams of water per square meter every hour.

The skin's ability to retain this moisture depends on the lipid bilayer. This is a layer of fats located between the dead skin cells. Moisturizers work by modifying the rate of this water loss through specific active ingredients.

Active ingredients in moisturizers generally fall into two categories: occlusives and humectants. Occlusives are hydrophobic, meaning they repel water. They form a coating on the surface of the skin to keep moisture from escaping. The level of occlusion depends on the product's consistency. Ointments are more occlusive than aqueous creams, which are more occlusive than lotions.

For example, applying a layer of petrolatum can reduce water loss by 50% to 75% for several hours.

Humectants work differently because they are hydrophilic, which means they attract water. These ingredients absorb moisture from the humid air when humidity is above 70%. They can also draw water from the deeper layers of the skin up to the surface. Because this can reduce hydration in lower layers, humectants are often combined with occlusives. This combination ensures the skin stays hydrated both at the surface and underneath. Many moisturizers also contain water to act as a temporary hydration agent.

There are many different types of ingredients used in these formulations. Petrolatum is one of the most effective, though its oily texture is sometimes unpopular. Many products use mineral oils and waxes because they are not prone to oxidation or rancidity. This makes them more stable than vegetable oils.

Recently, manufacturers have used more plant-based emollients from renewable sources. These include coconut oil, avocado oil, corn oil, and shea butter. These botanical esters can provide multiple functions, such as pigment wetting and lubrication.

Moisturizers serve many medical and practical purposes. They are used to treat skin diseases like psoriasis, ichthyosis vulgaris, and xerosis. They also help manage pruritus, which is itching, in atopic dermatitis.

Many moisturizers act as vehicles, or bases, for topical medications like Whitfield's ointment. You can also find moisturizing agents in sunscreens, shaving creams, and even disposable diapers. While some products claim to reduce wrinkles, many such claims lack strong scientific evidence.

However, there are important safety considerations to keep in mind. Over-moisturization can occur if products are applied too frequently. This might allow foreign substances to penetrate the skin, causing contact dermatitis or infections. Additionally, aromas or food additives like coconut milk can trigger immune reactions. The American Academy of Allergy, Asthma, and Immunology warned in 2014 that natural ingredients could introduce new food allergies. Finally, paraffin-based products pose a fire risk. In the U.K., paraffin was linked to 50 fire incidents between 2010 and 2018, many of which were fatal.

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