Worker bees collect flower nectar and store it inside their bodies in a specialized stomach called the honey stomach. The honey stomach is a separate entity from the bee's actual stomach and serves as a “satchel” or carrying container for transport back to the hive. Enzyme secretions from glands are then mixed with the nectar; these enzymes begin to break down the sucrose in nectar to simpler sugars.

Nectar can be comprised of up to 70% water. Much of this water must evaporate to get the viscous consistency of honey to which we are accustomed. Eventually, the water content of the nectar solution will decrease to around 17%, significantly reduced from the original content. This conversion of watery nectar to syrupy honey takes approximately 24-72 hours. The final water content of honey is a crucial factor in why it doesn’t spoil; its water content is far lower than that of bacteria or fungi.

Honey also has a low water activity; this is a measure of the amount of water in a substance available to sustain microbial growth. Water activity is measured on a scale of 0 to 1, with most mold and bacteria rendered unable to grow when water activity is below 0.75. The water activity of honey is around 0.60. Its low water content dehydrates bacteria, making honey resistant to spoiling.

Acidity also helps honey avoid spoiling. Average honey pH is around 4; this acidity is contributed to by various acids such as formic acid and citric acid as well as gluconic acid, produced by the action of bee enzymes on some of the glucose molecules in the honey. Acidity serves to boost honey’s antibacterial properties further since many bacteria thrive in neutral rather than acidic conditions. Hydrogen peroxide is also formed by the production of gluconic acid which can inhibit the growth of bacteria.

Now that we’ve determined that honey is a water-soluble raw material which naturally contains a small amount of water, this helps demystify the formulation process a bit. Honey cannot blend into oil-based formulations like lotions or lip balms without the use of an emulsifier.

Despite honey possessing natural anti-bacterial properties, it is not resistant to all forms of bacteria and microbes, such as botulism. Botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium Clostridium botulinum. Honey can contain botulism spores, and these spores release a toxin that can sicken adults and poison infants. The US Center for Disease Control recommends that infants under the age of 12 months should not be exposed to honey since they are most at risk due to an immature immune system. Botulism can also be introduced into the body through wounds on the skin. Heating honey to more than 85 °C (185 °F) for longer than five minutes can kill Clostridium botulinum but does not destroy or eradicate botulism spores. For these reasons, cosmetics containing honey in its natural, unaltered state should carry a warning label stating the product is not for use on children under the age of 12 months.

Although honey has been shown to be self-preserving in many cases, once other components are added to a formulation, self-preserving properties are diminished as the percentage of honey in the product decreases. However, the higher the percentage of honey in a formulation, the stickier and more viscous the final product which creates a different set of challenges. It is surmisable that a high proportion of honey could produce a self-preserving cosmetic, and in some instances, this is true due to something called hurdle technology.

Hurdle technology is defined as the calculated combination of different preservation factors (hurdles) to deteriorate the growth of microorganisms. Adherence to good manufacturing practices, carefully selected packaging, cautious choice of the type of emulsion, low water activity, and low or high pH values are significant variables for controlling microbial growth in cosmetic formulations. Hurdle technology isn’t new, it’s been around since the 1970’s in the food industry and has been re-popularized due to pressure by special interest groups and consumer demand for more natural preservation options.

Control of microbial growth can usually be carried out by limiting the availability of water, making anhydrous formulations a popular choice for formulators. Although many yeasts and molds can tolerate acid pH conditions (pH <4), many microorganisms are injured or stressed by extreme pH conditions (pH <4 or >10). However, extreme pH alone should not be the goal when creating a hostile environment because excess acidity or alkalinity may make some leave-on products harsh or irritating.

Honey contains carbohydrates, proteins, amino acids, vitamins, minerals, antioxidants and other compounds. Many enzymes, including invertase, glucose oxidase, catalase, and acid phosphorylase are also present in honey. It also contains 18 free amino acids, the most abundant of which is proline. Proline is involved in the body's production of collagen and cartilage and used in anti-aging and cosmetic formulas.

Honey also contains trace amounts of many B-vitamins and vitamin C. Minerals like calcium, iron, zinc, potassium, phosphorous, magnesium, selenium, chromium and manganese are also in honey. Flavonoids are the leading group of antioxidants in honey, with the flavanone pinocembrin being unique to honey and bee propolis. The darker the color of natural honey, the higher antioxidant properties it possesses.

Luckily, there are many derivatives of honey that are safe for use in cosmetics geared towards all age groups. So, there is no need to play roulette with honey in a formulation. One such ingredient that is becoming popular in natural skincare is gluconolactone. Considered a next-generation alpha hydroxy acid (AHA), gluconolactone is a polyhydroxy acid (PHA) that is present in bees' honey. It is intended for use with all skin types, including sensitive skin, and is non-irritating with antioxidant properties. Formulations containing gluconolactone may even smooth skin texture. Gluconolactone can be found in the alternative preservatives Geogard Ultra® and NataPres™.

Glucono Delta Lactone is another polyhydroxy acid (PHA) that is available in its natural state (gluconic acid) in honey and royal jelly. Gluconic acid is a molecule of glucose in which the aldehyde function is oxidized to an acid function. Bees do this through enzymatic action and in fermented products like wine and kombucha, microorganisms do it.

Cocoyl Honeyate, another honey-derived ingredient provides gentle sebum control as well as preventing dryness, promoting clear, smooth skin with an even tone and a matte finish, used in color cosmetics as a mattifier.

Melhydran™ LS 9876 is another raw material based on honey extract, obtained by gentle purification of natural honey. It is high in oligosaccharides, organic acids, amino acids, and minerals. Beneficial in personal care products with honey claims, moisturizing skin and hair care, baby care, and sensitive skin type products.

Because the use of honey in cosmetic applications tends to be popular in natural formulations or if less-processed is more your forte, honey extract and honey powder are readily available and very easy to add to formulations. It is also worthy of note that honey derives from living beings (bees), so it is not suitable for most vegans and should be excluded from formulations marketed to those following a vegan lifestyle.

References:

1. Varvaresou A, Papageorgiou S, Tsirivas E, Protopapa E, Kintziou H, Kefala V,
Demetzos C. Self-preserving cosmetics. Int J Cosmet Sci. 2009 Jun;31(3):163-75.
doi: 10.1111/j.1468-2494.2009.00492.x. Epub 2009 Mar 19. Review. PubMed PMID:
19302511.

2. Botulism Prevention: https://www.cdc.gov/botulism/prevention.html

3. Missio da Silva, P. et al. Honey: Chemical composition, stability and authenticity. Food Chemistry. 2016 April; Vol 196: 309-323. https://doi.org/10.1016/j.foodchem.2015.09.051

4. Kabara, Jon J. Hurdle Technology: Are Biocides Always Necessary For Product Protection? J. Appl. Cosmetol. 17, 102-108 (July/September 1999)