Moisturizer Explained

A moisturizer, or emollient,[1] is a cosmetic preparation used for protecting, moisturizing, and lubricating the skin. These functions are normally performed by sebum produced by healthy skin.[2] The word "emollient" is derived from the Latin verb mollire, to soften.[3]

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. By regulating its water content, human skin naturally maintains a dry, easily shed surface as a barrier 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 between the dead skin cells.

Moisturizers modify the rate of water loss, with active ingredients of moisturizers falling into one of two categories: occlusives and humectants.[4]

Occlusives form a hydrophobic 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. Water loss through the skin is normally about 4–8 g/(m2⋅h). A layer of petrolatum 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 are hydrophilic and absorb water. They absorb water from humid air (when >70% humidity) to moisturize the skin. More commonly, however, they draw out water from the dermis into the epidermis, making deeper skin dryer.[5] When used in practical applications, humectants are combined with occlusives.[6] Moisturizers commonly contain water, which acts as a temporary hydration agent.

Kinds

There are many different types of moisturizers. Petrolatum is one of the most effective moisturizers, although it can be unpopular due to its oily consistency.[7] [8]

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, and other oils.

Moisturizers may also be available as lotions, creams, ointments, bath oils, or soap substitutes.

Mineral oils and waxes are not prone to oxidation or rancidity.[9] For this reason, they have essentially replaced vegetable oils in emollients and topical medication.

Moisturizer cosmetics may additionally contain antioxidants, ceramides, emulsifiers, fragrances, penetration enhancers, preservatives, and solvents. Some products are marketed as having anti-wrinkle and skin enhancement effects. Many plant and animal extracts have been claimed to impart skin benefits, but such claims are presented with little scientific evidence.

Use

Moisturizers are used for the treatment of certain skin diseases, such as psoriasis, ichthyosis vulgaris, xerosis, and pruritus in atopic dermatitis. More often, they are bases or vehicles for topical medication, such as in Whitfield's ointment. They are often combined with humectants, such as salicylic acid and urea.

Moisturizers are also widely used in sunscreens, antiperspirants, skin cleansers, shaving creams, aftershaves, and hair tonics.

Moisturizers are used in disposable diapers to prevent dry skin and diaper dermatitis.

Moisturizers show some beneficial effects in treating atopic dermatitis (eczema). Using moisturizers helps to improve skin comfort and may reduce disease flares.[10] [11] They can be used as leave-on treatments, bath additives, or soap substitutes. There are many different moisturizer products, but the majority of leave-on treatments (from least to most greasy) are one of the following: lotions, creams, gels, or ointments. As none of the different types of moisturizers are more effective than the others, people with atopic dermatitis need to choose one or more products according to their age, affected body site, climate/season, and personal preference.[12] However using moisturizers daily in infants during the first year of life does not help to prevent the development of atopic dermatitis, and might even increase the risk of skin infections.[13] [14]

Potential health risks

Over-moisturization

Persistent moisturization to the skin via water contact may contribute to an allergic reaction or contact dermatitis. This could allow foreign objects to penetrate the skin.

Changes in the skin's normal ecological environment–either atop or within the skin–can also allow for the overgrowth of pathogens.[15]

Allergens

Aromas or food additives in moisturizers may trigger an immune reaction, including development of an allergy.

There is currently no regulation over use of the term "hypoallergenic". In fact, some pediatric skin products marketed as hypoallergenic contained allergens.[16] [17]

Those with eczema are especially vulnerable to allergic reaction with lotions and creams, as their compromised skin barrier allows preservatives to bind with and activate immune cells.[18]

The American Academy of Allergy, Asthma, and Immunology 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, potentially causing an allergic reaction upon later consuming such foods.[19] A paper published in 2021 noted 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.[20]

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.[21] 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.[22] The Medicines and Healthcare products Regulatory Agency (MHRA) released a warning in 2008 about the flammability of paraffin-based products.[23] MHRA recommends that regular paraffin users change their sheets regularly, refrain from smoking and/or bringing open flames near paraffin-coated people or objects.[24] MHRA also recommends that skin creams containing any paraffin have a flammability warning on the packaging.[25]

Brands of moisturizers

See also

Notes and References

  1. Book: Marks . Ronald . Emollients . January 1997 . CRC Press . 978-1-85317-439-1 . 1 . 31 December 2020 . en . 11 April 2023 . https://web.archive.org/web/20230411114420/https://books.google.com/books?id=-5ERJNzBQ9gC . live .
  2. Book: MacDonald . Matthew . Your Body: The Missing Manual . 21 July 2009 . "O'Reilly Media, Inc." . 978-1-4493-9201-7 . 22 . en . 19 March 2023 . 1 October 2023 . https://web.archive.org/web/20231001100316/https://books.google.com/books?id=WGYoDwAAQBAJ&q=sebum . live .
  3. Book: Schueller . Randy . Romanowski . Perry . Conditioning Agents for Hair and Skin . 24 July 2020 . CRC Press . 978-1-000-11037-1 . 111 . en . 19 March 2023 . 11 April 2023 . https://web.archive.org/web/20230411114419/https://books.google.com/books?id=mIXxDwAAQBAJ&dq=emollient+mollire+to+soften&pg=PA111 . live .
  4. Web site: Duffill . Mark . Oakley . Amanda . Emollients and moisturisers . dermnetnz.org . 31 December 2020 . 25 August 2023 . https://web.archive.org/web/20230825045713/https://dermnetnz.org/topics/emollients-and-moisturisers . live .
  5. Harwood . Anne . Nassereddin . Ali . Krishnamurthy . Karthik . Moisturizers . StatPearls . StatPearls Publishing . 31 December 2020 . 2020 . 31424755 . 28 January 2023 . https://web.archive.org/web/20230128195629/https://www.ncbi.nlm.nih.gov/books/NBK545171/ . live .
  6. Web site: Publishing . Harvard Health . Moisturizers: Do they work? . Harvard Health . February 2008 . 31 December 2020 . 20 September 2023 . https://web.archive.org/web/20230920001311/https://www.health.harvard.edu/staying-healthy/moisturizers-do-they-work . live .
  7. Sethi . Anisha . Kaur . Tejinder . Malhotra . SK . Gambhir . ML . Moisturizers: The Slippery Road . Indian Journal of Dermatology . 2016 . 61 . 3 . 279–287 . 10.4103/0019-5154.182427 . 27293248 . 4885180 . 0019-5154. free .
  8. Web site: Publishing . Harvard Health . Choosing a good moisturizer for your skin . Harvard Health . 5 April 2018 . 31 December 2020 . 1 October 2023 . https://web.archive.org/web/20231001100959/https://www.health.harvard.edu/staying-healthy/choosing-a-good-moisturizer-for-your-skin . live .
  9. Chuberre . B. . Araviiskaia . E. . Bieber . T. . Barbaud . A. . Mineral oils and waxes in cosmetics: an overview mainly based on the current European regulations and the safety profile of these compounds . Journal of the European Academy of Dermatology and Venereology. 5–14 . 10.1111/jdv.15946 . November 2019. 33 . Suppl 7 . 31588613 . 203850745 . free .
  10. Ridd MJ, Roberts A, Grindlay D, Williams HC . October 2019 . Which emollients are effective and acceptable for eczema in children? . live . BMJ . 367 . l5882 . 10.1136/bmj.l5882 . 31649114 . 204882682 . https://web.archive.org/web/20230411114201/https://research-information.bris.ac.uk/ws/files/219950607/bmj.l5882.full.pdf . 2023-04-11 . 2023-04-11.
  11. van Zuuren. Esther J. Fedorowicz. Zbys. Christensen. Robin. Lavrijsen. Adriana PM. Arents. Bernd WM. 2017-02-06. Emollients and moisturisers for eczema. Cochrane Database of Systematic Reviews. Review. 2. 8. CD012119. 10.1002/14651858.cd012119.pub2. 28166390. 1465-1858. 6464068.
  12. 6 . Ridd MJ, Santer M, MacNeill SJ, Sanderson E, Wells S, Webb D, Banks J, Sutton E, Roberts A, Liddiard L, Wilkins Z, Clayton J, Garfield K, Barrett TJ, Lane JA, Baxter H, Howells L, Taylor J, Hay AD, Williams HC, Thomas KS . August 2022 . Effectiveness and safety of lotion, cream, gel, and ointment emollients for childhood eczema: a pragmatic, randomised, phase 4, superiority trial . The Lancet. Child & Adolescent Health . 6 . 8 . 522–532 . 10.1016/S2352-4642(22)00146-8 . 35617974 . 249024141 . free . free . 1983/e4009d3c-127f-4aa9-bf71-e40401b33eee.
  13. Eczema in children: uncertainties addressed . 2024-03-19 . NIHR Evidence . 10.3310/nihrevidence_62438 . en.
  14. Kelleher MM, Phillips R, Brown SJ, Cro S, Cornelius V, Carlsen KC, Skjerven HO, Rehbinder EM, Lowe AJ, Dissanayake E, Shimojo N, Yonezawa K, Ohya Y, Yamamoto-Hanada K, Morita K, Axon E, Cork M, Cooke A, Van Vogt E, Schmitt J, Weidinger S, McClanahan D, Simpson E, Duley L, Askie LM, Williams HC, Boyle RJ . November 2022 . Skin care interventions in infants for preventing eczema and food allergy . The Cochrane Database of Systematic Reviews . 2022 . 11 . CD013534 . 10.1002/14651858.CD013534.pub3 . 9661877 . 36373988 . Cochrane Skin Group.
  15. Marino. Christina. 2006. Skin Physiology, Irritants, Dry Skin and Moisturizers. Skin Physiology, Irritants, Dry Skin and Moisturizers. 2019-01-29. 2017-08-29. https://web.archive.org/web/20170829154832/http://www.lni.wa.gov/Safety/Research/Dermatitis/files/skin_phys.pdf. dead.
  16. Web site: Parsons. Julia. Protect children's skin from unregulated term 'hypoallergenic'. BAYLOR COLLEGE OF MEDICINE NEWS. 31 December 2015. 4 March 2016. https://web.archive.org/web/20160304073736/https://www.bcm.edu/news/skin-and-hair/protect-kids-from-unregulated-hypoallergenic. live.
  17. Schlichte. Megan J.. Katta. Rajani. Methylisothiazolinone: An Emergent Allergen in Common Pediatric Skin Care Products. Dermatology Research and Practice. 2014. 1–4. 10.1155/2014/132564. 25342949. 4197884. 2014. free.
  18. News: Doyle. Kathryn. Some skin creams bad news for eczema. Reuters. 31 December 2015. 2013-12-12. 2016-09-24. https://web.archive.org/web/20160924101858/http://www.reuters.com/article/us-skin-creams-eczema-idUSBRE9BB14720131212?. live.
  19. Web site: Graham. Melissa. Researchers find link between natural lotions, new food allergies. American Academy of Allergy, Asthma & Immunology. 31 December 2015. https://web.archive.org/web/20171109191313/http://www.aaaai.org/about-aaaai/newsroom/news-releases/natural-lotions. 2017-11-09.
  20. Web site: Frequent moisturization of infants can lead to food allergies . Medical News . 7 August 2022 . 4 March 2021 . 19 November 2023 . https://web.archive.org/web/20231119150759/https://www.news-medical.net/news/20210304/Frequent-moisturization-of-infants-can-lead-to-food-allergies.aspx . live .
  21. Web site: Emollients: new information about risk of severe and fatal burns with paraffin-containing and paraffin-free emollients . GOV.UK . 31 December 2020 . en . 8 November 2020 . https://web.archive.org/web/20201108141042/https://www.gov.uk/drug-safety-update/emollients-new-information-about-risk-of-severe-and-fatal-burns-with-paraffin-containing-and-paraffin-free-emollients . live .
  22. News: Fire tests show dangers of paraffin-based skin creams . BBC News . 31 December 2020 . 29 November 2021 . https://web.archive.org/web/20211129162633/https://www.bbc.com/news/av/uk-43009261 . live .
  23. Web site: Paraffin-based treatments: risk of fire hazard . GOV.UK . 31 December 2020 . en . 21 February 2022 . https://web.archive.org/web/20220221230533/https://www.gov.uk/drug-safety-update/paraffin-based-treatments-risk-of-fire-hazard . live .
  24. Web site: Paraffin-based skin emollients on dressings or clothing: fire risk . GOV.UK . 31 December 2020 . en . 4 February 2022 . https://web.archive.org/web/20220204083840/http://www.gov.uk/drug-safety-update/paraffin-based-skin-emollients-on-dressings-or-clothing-fire-risk . live .
  25. Web site: Goldberg . Adrian . Robinson . Ben . Skin creams containing paraffin linked to fire deaths . BBC News . 31 December 2020 . 19 March 2017 . 15 December 2020 . https://web.archive.org/web/20201215220258/https://www.bbc.com/news/uk-39308748 . live .

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