Editing Humectant

{{Short description|Water-absorbing substance used to keep things moist}}

A '''humectant''' {{IPAc-en|h|juː|ˈ|m|ɛ|k|t|ən|t}} is a [[hygroscopic]] (water-absorbing) [[Chemical substance|substance]] used to keep things moist.  They are used in many products, including food, cosmetics, medicines and pesticides. When used as a [[food additive]], a humectant has the effect of keeping moisture in the food.<ref>{{Cite book|url=https://books.google.com/books?id=1bzCYeHoJ8sC&q=humectant+food+additives&pg=PA343|title=The Encyclopedia of Nutrition and Good Health|last=Ronzio|first=Robert A.|date=2003-01-01|publisher=Infobase Publishing|isbn=9780816066308|pages=343|language=en}}</ref> Humectants are sometimes used as a component of [[antistatic]] coatings for [[plastic]]s.

A humectant attracts and retains the moisture in the air nearby via absorption, drawing the water vapor into or beneath the organism's or object's surface.<ref>{{cite web|url=http://www.thefreedictionary.com/humectant|title=humectant|access-date=17 November 2016|via=The Free Dictionary}}</ref><ref>{{cite web|url=http://www.wisegeek.org/what-is-an-humectant.htm|title=What is an Humectant? (with pictures)|access-date=17 November 2016}}</ref> This is the opposite use of a hygroscopic material where it is used as a [[desiccant]] used to draw moisture away.

In pharmaceuticals and cosmetics, humectants can be used in [[topical]] [[dosage form]]s to increase the solubility of a chemical compound's [[active ingredient]]s, increasing the active ingredients' ability to penetrate skin, or its activity time. This hydrating property can also be needed to counteract a dehydrating active ingredient (e.g., [[soap]]s, [[corticoid]]s, and some [[Alcohol (chemistry)|alcohol]]s), which is why humectants are common ingredients in a wide range of cosmetic and personal care products that make moisturization claims (e.g., [[hair conditioner]]s, [[body lotion]]s, face or body cleansers, [[Lip balm|lip balms]], and eye creams).

==Chemistry==
A humectant is often a molecule with several [[hydrophilic]] groups, most often [[hydroxyl group]]s; however, [[amine]]s and [[carboxyl group]]s, sometimes [[ester]]ified, can be encountered as well (its affinity to form [[hydrogen bond]]s with molecules of water is the crucial trait).

==Examples==
Examples of some humectants include:
{{div col|colwidth=30em}}
* [[Propylene glycol]], [[hexylene glycol]], and [[butylene glycol]]
* [[Aloe vera]] gel
* [[Alpha hydroxy acid]]s such as [[lactic acid]]
* [[Egg yolk]] and [[egg white]]
* [[Glyceryl triacetate]]
* [[Honey]]
* [[Lithium chloride]]
* [[Molasses]]
* Polymeric [[polyol]]s  such as [[polydextrose]]
* [[Quillaia]]
* [[Sodium hexametaphosphate]] E452i
* [[Sugar alcohol]]s (sugar polyols) such as [[glycerol]], [[sorbitol]], [[xylitol]], [[maltitol]]
* [[Urea]]
* [[Castor oil]]
{{div col end}}

==Uses==
A humectant is a substance that is used to keep products moisturized and affects the preservation of items, which can be used in cosmetic products, food and tobacco. A
humectant-rich formulation contains simple alcoholic sugar that can increase skin hydration and helps to remove and reduce thickness of skin.<ref>{{cite journal |pmid=23521561 | doi=10.1111/srt.12066 | volume=19 | issue=4 | title=The influence of a humectant-rich mixture on normal skin barrier function and on once- and twice-daily treatment of foot xerosis. A prospective, randomized, evaluator-blind, bilateral and untreated-control study | year=2013 | journal=Skin Res Technol | pages=438–45 |vauthors=Lodén M, von Scheele J, Michelson S | s2cid=25361259 }}</ref>

===Food additives===
Some common humectants used in food are [[honey]] and glucose syrup both for their water absorption and sweet flavor.<ref name="Farris, S. S. 2008">{{cite journal |author1=Farris S. S. |author2=Piergiovanni L. L. |author3=Limbo S. S. | year = 2008 | title = EFFECT OF BAMBOO FIBRE AND GLUCOSE SYRUP AS NEW INGREDIENTS IN THE MANUFACTURE OF AMARETTI COOKIES | journal = Italian Journal of Food Science | volume = 20 | issue = 1| pages = 75–90 }}</ref> Glucose syrup also helps to retain the shape of the product better than other alternatives, for a longer period of time. In addition, some humectants are recognized in different countries as good [[food additives]] because of the increase in nutritional value that they provide, such as [[sodium hexametaphosphate]].<ref>Broad Chemicals as Food Additives. (2010). ''China Chemical Reporter'', 21(4), 12.</ref>

In order to gauge a compound's humectancy, scientists will put it through a series of tests, often involving water absorption. In tests involving toothpaste, the process is also coupled with a sweetness test and a crystallization test. When humectancy is being assessed in different products, testers will compare the results to other humectants that are already used in those products, in order to evaluate efficiency.<ref>{{cite journal | author = Lu Y. Y. | year = 2001 | title = Humectancies of d-tagatose and d-sorbitol | journal = International Journal of Cosmetic Science | volume = 23 | issue = 3| page = 178 | doi = 10.1046/j.1467-2494.2001.00084.x | pmid = 18498471 | s2cid = 206173511 }}</ref>

Some of these humectants are seen in non-ionic [[polyols]] like [[sucrose]], [[glycerin]] or [[glycerol]] and its triester ([[triacetin]]). These humectant food additives are used for the purpose of controlling [[viscosity]] and texture. Humectants also add bulk, retain moisture, reduce water activity, and improve softness. A main advantage of humectant food additives is that, since they are non-ionic, they are not expected to influence any variation of the [[pH]] [[aqueous]] systems.<ref>{{cite book|chapter= Preservatives|doi=10.1002/9781118274132.ch15
| publisher= Wiley |title=Chemistry of Food Additives and Preservatives|pages=224–243|year = 2012|isbn = 9781118274132 | author-first=Titus A. M. | author-last=Msagati  }}</ref>

Glycerol or glycerin humectants undergo a pretreatment process using [[saponification]], bleaching, ion exchange exclusion, both cationic and ionic ion exchanges, vacuum flash evaporation, thin film distillation, and heating to produce a 100% pure glycerol.<ref>Msagati, Titus A. M. ''The Chemistry of Food Additives and Preservatives''. Oxford: Wiley-Blackwell, 2013. PDF.</ref>

Humectants are used in stabilization of food products and lengthening shelf life through food and moisture control. The available moisture determines [[microbial]] activity, physical properties, sensory properties and the rate of chemical changes, that if not controlled, are the cause of reduced shelf life.<ref>{{cite journal |author1=Severini C. |author2=Corbo M. |author3=Derossi A. |author4=Bevilacqua A. |author5=Giuliani R. | year = 2008 | title = Use of humectants for the stabilization of pesto sauce | journal = International Journal of Food Science & Technology | volume = 43 | issue = 6| pages = 1041–1046 | doi = 10.1111/j.1365-2621.2007.01560.x }}</ref> Examples are dry [[cereal]] with semi-moist [[raisins]], [[ice cream]] in a cone, [[chocolate]], [[hard candy]] with liquid centers and [[cheese]]. Humectants are used to stabilize the moisture content of foodstuffs and are incorporated as food additives. Humectants are also used in military technology for the use of [[MRE]]s and other military rations.<ref>{{cite news|url=https://www.bbc.com/news/blogs-magazine-monitor-26255153|title=The military pizza that lasts for three years|date=19 February 2014|access-date=17 November 2016|work=BBC News}}</ref>
A number of food items always need to be moist. The use of humectants reduces the available water, thus reducing bacterial activity. They are used for safety issues, for quality, and to have a longer shelf-life in food products.

An example of where humectants are used to keep food moist is in products like [[toothpaste]]<ref>{{cite journal | last1 = Lu | first1 = Y. Y. | year = 2001 | title = Humectancies of d-tagatose and d-sorbitol | journal = International Journal of Cosmetic Science | volume = 23 | issue = 3| pages = 175–81 | doi=10.1046/j.1467-2494.2001.00084.x| pmid = 18498471 | s2cid = 206173511 }}</ref> as well as certain kinds of [[cookies]]. Regional kinds of cookies often use humectants as a binding agent in order to keep moisture locked into the center of the cookie rather than have it evaporate out.<ref>{{cite journal |author1=Farris S. S. |author2=Piergiovanni L. L. |author3=Limbo S. S. | year = 2008 | title = EFFECT OF BAMBOO FIBRE AND GLUCOSE SYRUP AS NEW INGREDIENTS IN THE MANUFACTURE OF AMARETTI COOKIES | journal = Italian Journal of Food Science | volume = 20 | issue = 1| page = 77 }}</ref> Humectants are favored in food products because of their ability to keep consumable goods moist and increase shelf-life.<ref name="Farris, S. S. 2008"/>

===Cosmetics===
Humectants are frequently used in cosmetics as a way of increasing and maintaining moisture in the skin and hair, in  products including shampoo, conditioner, frizz serum, lotions, creams, lip treatments, cleansers, after-sun lotion, and some soaps or body lotions. As hygroscopic moisturizers, humectants work by attracting water to the upper layer of the skin (stratum corneum).<ref>Making Cosmetics, Inc. http://www.makingcosmetics.com/articles/13-humectants-moisturizing-agents-in-cosmetics.pdf {{Webarchive|url=https://web.archive.org/web/20150319054049/http://www.makingcosmetics.com/articles/13-humectants-moisturizing-agents-in-cosmetics.pdf |date=2015-03-19 }} (Accessed 5/10/14{{Clarify|reason=ambiguous date format|date=November 2016}})</ref> All humectants have common hydroxyl groups which allow them to participate in hydrogen bonding and attract water. This process attracts moisture from the outer layer of the skin or, in high humidity, from the atmosphere. The moisture is then trapped against the [[Epidermis (skin)|epidermis]] or the shaft of the hair, depending on where the humectant is applied. Various humectants have different ways of behaving because they differ in water binding capacity at different humidities.<ref>Elsner, P., Maibach, H. (2005) Cosmecuticals and Active Cosmetics – Drugs Versus Cosmetics.</ref>

Humectants used in cosmetics include [[triethylene glycol]],<ref>{{cite journal | year = 2006 | title = Final Report on the Safety Assessment of Triethylene Glycol and PEG-41 | journal = International Journal of Toxicology | volume = 25 | issue = 2_suppl| pages = 121–138 | doi = 10.1080/10915810600964642 | pmid = 17090481 | s2cid = 208154098 }}</ref> [[Tripropylene|tripropylene glycol]],<ref>{{cite journal |author1=Fiume M. M. |author2=Bergfeld W. F. |author3=Belsito D. V. |author4=Hill R. A. |author5=Klaassen C. D. |author6=Liebler D. |author7=Andersen F. | year = 2012 | title = Safety Assessment of Propylene Glycol, Tripropylene Glycol, and PPGs as Used in Cosmetics | journal = International Journal of Toxicology | volume = 31 | issue = 5| pages = 245S–260S | doi = 10.1177/1091581812461381 |pmid=23064775 |s2cid=24754435 |doi-access=free }}</ref> [[propylene glycol]], and [[Polypropylene glycol|PPGs]]. Other popular humectants in cosmetics include [[glycerin]], [[sorbitol]] (sugar alcohol), hexylene and butylene glycol, urea, and collagen.<ref>{{cite journal |author1=Peng Y. |author2=Glattauer V. |author3=Werkmeister J. A. |author4=Ramshaw J. A. M. | year = 2004 | title = Evaluation for collagen products for cosmetic application | journal = International Journal of Cosmetic Science | volume = 26 | issue = 6| page = 313 | doi = 10.1111/j.1467-2494.2004.00245_2.x |citeseerx=10.1.1.504.6688 }}</ref> Glycerin is one of the most popular humectants used because it produces the desired result fairly frequently and is low in cost. A category of humectants called nanolipidgels allow skin to retain moisture, but also possess antifungal properties.<ref>{{cite journal|title=Nanolipidgel for enhanced skin deposition and improved antifungal activity|first1=Preeti|last1=Wavikar|first2=Pradeep|last2=Vavia|date=1 March 2013|journal=AAPS PharmSciTech|volume=14|issue=1|pages=222–233|doi=10.1208/s12249-012-9908-y|pmid=23263751|pmc=3581678}}</ref> Scientists are also working to discover different types of humectants; a study published in 2011 concluded that extracts from wine cakes have the potential to be used as a humectant in cosmetics.<ref>{{cite journal |author1=Chiang H. |author2=Ko Y. |author3=Shih I. |author4=Wen K. | title = Development of Wine Cake as a Skin-Whitening Agent and Humectant | journal = Journal of Food & Drug Analysis | volume = 19 | issue = 2| pages = 223–229 }}</ref>

Humectants have been added to skin moisturizing products to treat [[xerosis]]. Some moisturizers tend to weaken the skin barrier function, but studies on xerosis have proven that moisturizers containing humectants increase desired moisturizing effects on the affected area without damage to the skin barrier function.<ref name=Loden>{{cite journal | author = Lodén, M., Scheele, J., & Michelson, S. | date = 2013 | title = The influence of a humectant-rich mixture on normal skin barrier function and on once- and twice-daily treatment of foot xerosis. A prospective, randomized, evaluator-blind, bilateral and untreated-control study | journal = Skin Research & Technology | volume = 19 | issue = 4 | pages = 438–445}}</ref> In this xerosis treatments study, some "smarting and stinging" was also reported from the use of humectant-rich treatment products.<ref name=Loden/>

When the humectant glycerol was added to soaps for the cleansing of wounds, similar effects were found. There was an increase in moisture in the areas that the soap was applied, however, "further consideration of conditioning the use of glycerol to improve the absorption of exudates from wounds for an advanced wound healing is needed."<ref>{{cite journal | author = Gwon, H., Lim, Y., Nho, Y., & Baik, S. | date = 2010 | title = Humectants effect on aqueous fluids absorption of γ-irradiated PVA hydrogel followed by freeze thawing | journal = Radiation Physics & Chemistry | volume = 79 | issue = 5 | pages = 650–653 | doi=10.1016/j.radphyschem.2009.12.011| bibcode = 2010RaPC...79..650G }}</ref> The healing properties of humectants are therefore uncertain.

Humectants are also added to toothpaste (dentifrice) to stop the product drying out and cracking in the tube.  Sorbitol is commonly used as this also contributes a sweet flavour to the toothpaste without contributing to tooth decay.<ref>{{Cite web|url=https://www.colgate.com/en-us/oral-health/basics/selecting-dental-products/what-is-in-toothpaste-five-ingredients-and-what-they-do-0814|title=What is in Toothpaste? Five Ingredients and What They do}}</ref>

===Tobacco products===
{{cleanup |reason=Needs rewrite to untangle cigarettes vs. e-cigs (see talk page) |date=December 2019}}
Humectants are used in the manufacturing of some [[tobacco]] products, such as [[cigarettes]], [[e-cigarettes]], and self-rolled tobacco. They are used to control and maintain the moisture content of the cut tobacco filler and add flavor. Humectants are vital to the creation of cigarettes.<ref>{{cite journal |author1=Heck D. |author2=Gaworski C. |author3=Rajendran N. |author4=Morrissey R. | year = 2002 | title = Toxicologic Evaluation of Humectants Added To Cigarette Tobacco: 13-Week Smoke Inhalation Study | journal = Inhalation Toxicology | volume = 14 | issue = 11| pages = 1135–1152 | doi = 10.1080/08958370290084827 |pmid=12454795 |s2cid=25700504 }}</ref> In an examination of waterpipe smoking, researchers worked to identify substances such as [[formaldehyde]], [[acetaldehyde]], and [[acrolein]] in the smoke of a waterpipe, discovering that the value of formaldehyde detected in one smoking session was five times higher than that of a regular cigarette. This data demonstrated that increasing amounts of humectants in the unburned tobacco lowered the temperature in the waterpipe head during smoking, so that considerable amounts of toxic substances were present. Further, e-cigarettes produce aerosol by heating a humectant containing nicotine without burning tobacco. Those "vaping" then inhale the aerosol and receive nicotine.<ref>[http://www.unboundmedicine.com/evidence/ub/citation/22707202/Waterpipe_smoking:_the_role_of_humectants_in_the_release_of_toxic_carbonyls_ Schubert, J. Waterpipe smoking: the role of humectants in the release of toxic carbonyls. ''Archives of Toxicology'', 86, 1309–1316]</ref>

The main health concern regarding e-cigarettes is that their production is not regulated, and there is immense uncertainty of quality control during manufacturing. Self-rolled tobacco contains more humectants, which are added to tobacco to improve taste and keep from drying out. As the humectants burn, they release chemicals such as acrolein. Humectants are found in most cigarettes and are considered one of the most dangerous chemicals found in tobacco.<ref>{{Cite web |url=http://www.smokefreeoxfordshire.nhs.uk/why-stop-smoking/smoking-its-dangers/roll-ups/ |title=Roll-ups. 2012, January 1. Retrieved May 11, 2014 |access-date=June 9, 2014 |archive-date=August 31, 2014 |archive-url=https://web.archive.org/web/20140831150024/http://www.smokefreeoxfordshire.nhs.uk/why-stop-smoking/smoking-its-dangers/roll-ups/ |url-status=dead }}</ref>

However, there have been conflicting claims about the degree to which these products warrant a health concern. In a literary study of e-cigarette health risks, 388 different symptoms were reported; mouth and throat concerns generated more negative symptoms than any other group.<ref>{{cite journal|title=Health-Related Effects Reported by Electronic Cigarette Users in Online Forums|first1=My|last1=Hua|first2=Mina|last2=Alfi|first3=Prue|last3=Talbot|date=1 January 2013|volume=15|issue=4|doi=10.2196/jmir.2324|pmid=23567935|pmc=3636314|journal=Journal of Medical Internet Research|pages=e59 |doi-access=free }}</ref> There are not enough studies or sufficient evidence to suggest that products, particularly the contaminants of the aerosol in e-cigarettes, produce health risks at a concerning level. More research is currently being conducted to find the true dangers of the use of humectants in cigarettes.<ref>{{cite journal | author = Burstyn  | year = 2014 | title = Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks | journal = BMC Public Health | volume = 14 | page = 18 | pmc=3937158 | pmid=24406205 | doi=10.1186/1471-2458-14-18 | doi-access = free }}</ref>

==References==
{{reflist|2}}

[[Category:Food additives]]
[[Category:Excipients]]