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There are many types of honey with varying properties. Most people like to eat it but some of us also like to put it on our  skin.  Most people also know about Manuka honey and its purported anti bacterial properties. Lesser known is Sidr honey which comes from the nectar of the Sidr tree in Yemen and is rare, limited in supply and  expensive.   But, honey in general has been studied extensively, particularly its use in wound healing.  There appears to be a fascination around the anti bacterial nature of honey, in the available literature.  So what do we know about honey, how is it defined and classified; and how can honey be beneficial in skincare? First lets have a look at what honey is and where it comes from.

What is honey?

Honey is the natural sweet substance produced by honey bees from nectar or blossoms or from the secretion of living parts of plants or excretions of plants, which honey bees collect, transform, and combine with specific substances of their own to ripen and mature1. It is also defined as the nectar and saccharine exudation of plants, gathered, modified and stored as honey in the honeycomb by honeybees, Apis melifera'' (P. Olaitan et al., 2007)

How is honey classified under EU law?

The EU Directive defines honey as, "the natural sweet substance produced by Apis mellifera bees from the nectar of plants or from secretions of living parts of plants or excretions of plant-sucking insects on the living parts of plants, which the bees collect, transform by combining with specific substances of their own, deposit, dehydrate, store and leave in honeycombs to ripen and mature." In addition to the above honey has to meet certain "composition and quality  criteria" to be called honey.   

To be placed on the market it must:

1) not have any additions other than honey;

2) as far as possible, be free from organic or inorganic matter foreign to its composition;

3) not have any foreign tastes or odours, signs of fermentation or artificially changed acidity or have been heated in such a way that the natural enzymes have been either destroyed or significantly inactivated. Honey must also  comply with the following physico-chemical characteristics:

1) fructose and glucose content in blossom honey not less than 60 g/100 g; in honey dew honey and blends of honeydew honey with blossom honey not less than 45 g/100 g;

2) sucrose content not more than 5 g/100 g; in honey obtained from false acacia (Robinia pseudoacacia), alfalfa (Medicago sativa), Menzies Banksia (Banksia menziesii), French honeysuckle (Hedysarum), red gum (Eucalyptus camadulensis), leatherwood (Eucryphia lucida), dwarf leatherwood (Eucryphia milliganii) or citrus (Citrus spp.) not more than 10 g/100 g; in honey obtained from lavender (Lavandula spp.) or borage (Borago officinalis) not more than 15 g/100 g;

3) moisture content not more than 20 %; in heather (Calluna) and baker’s honey not more than 23 %; in baker’s honey from heather not more than 25 %;

4) water-insoluble content not more than 0.1 g/100 g; in pressed honey not more than 0.5 g/100 g;

5) electrical conductivity not more than 0.8 millisiemens per centimetre; in honeydew and chestnut honey and blends of these not less than 0.8 mS/cm, except for honey obtained from the strawberry tree (Arbutus unedo), bell heather (Erica), eucalyptus, lime (Tilia spp.), ling heather (Calluna vulgaris), manuka or jelly bush (Leptospermum) or the tea tree (Melaleuca spp.);

6) free acid content not more than 50 milli-equivalents per 1 000 grams; in baker’s honey not more than 80 milli-equivalents per 1 000 grams;

7) diastase activity after processing and blending (Schade scale) not less than 8, except baker’s honey; diastase activity in honeys with low natural enzyme content (e.g. citrus honeys) and a hydroxymethylfurfural (HMF) content of not more than 15 mg/kg, not less than 3;

8) hydroxymethylfurfural content after processing and blending not more than 40 mg/kg, except for baker’s honey and having regard to the HMF content referred to in 7 above; in honeys from regions with a tropical climate and blends of these honeys not more than 80 mg/kg. (The Honey (England) Regulations 2015)

How is honey made?

We all know that honey comes from bees. But, by what mechanism does nectar become honey?

There are different types of bees in a colony, each with their own distinct function for the hive.  Forager bees that collect nectar (the sweet watery sugary substance found in flowers) from nearby flowering plants. These foragers drink the nectar and hold it in their stomachs or 'crop' They transport it back to the hive where they are met by the 'processor' bee.  The foragers regurgitate the nectar directly into the  stomach of the processor bee near the entrance of the hive. The forager then carries on his task of collecting more nectar and the processor takes the nectar to the honey comb, near the top of the hive, regurgitating it into the hexagonal wax cell where it is left to ripen. Crucial in the processing of honey is the enzyme invertase.  The processor bee adds invertase every time they regurgitate the nectar.  This breaks the sucrose - contained in the nectar - down into simple sugars; mainly glucose and fructose.    

Once the honey is in the hive it needs to ripen. Ripening is the process whereby the nectar, which contains 70% water is reduced to around an 17-23% water and sugar solution. Again, honey bees are crucial in the evaporation of water.  They frantically fan their wings, creating airflow in the hive and around the honeycomb which helps to evaporate the water from the nectar creating a highly viscous solution. Once the nectar has ripened into honey, it contains such a small amount of water and such a high amount of sugars that microbes can not grow in it (this is not to say that they do not remain dormant).  At this point the bees will cap the honey with wax to stop any moisture getting in and causing it to spoil.

Water activity and water content of honey

"Due to the high content of monosaccharides (fructose and glucose) and relatively low moisture content, the water activity of honey is usually, but not always, below 0.60 which is enough to inhibit the growth of osmotolerant yeasts (Beckh, Wessel, & Lüllmann, 2004; Ruegg & Blanc, 1981; Zamora & Chirife, in press)."

How is honey beneficial to skin?  

Honey is beneficial in a number of ways - it has humectant, antibacterial, occlusive qualities and is a natural exfoliant due to its natural pH and polyhydroxy acid; gluconic acid.  It is thought that for this reason honey has been used traditionally for wound healing and has re-emerged as a strategy for treating wounds infected with bacteria resistant to antibiotics.

Natural antibacterial 

The natural anti bacterial properties of honey have been studied extensively and it is clear that honey is a strong antimicrobial.  Research has found that the anti bacterial quality is most likely from the hydrogen peroxide, its low pH and the presence of gluconic acid. Hydrogen peroxide is formed from the glucose oxidase, an enzyme that comes from bees when it regurgitates the honey into the honeycomb.  It plays an important part in forming gluconolactone which then transforms into gluconic acid and hydrogen peroxide. The gluconic acid is the main acid in honey and accounts in part to its acidic pH. Although  gluconolactone is not present in honey once it has ripened however, if diluted gluconolacone  becomes active again (http://www.airborne.co.nz/enzymes.shtml).

Natural PHA  

The polyhydroxy acid found in honey is gluconic acid. There are other acids, namely alpha hydroxy acids such as  citric and malic acid which help keep the pH of honey to on average of about 3.9.   Polyhydroxy acids (PHAs) have a similar effect as alpha hydroxy acid, including exfoliation, skin soothing, anti ageing and anti - photo ageing effects without causing irritation that AHA's may cause. They have been found compatible with sensitive skin including rosacea and atopic dermatitis and can be used after cosmetic surgery.  PHA's can also help with moisturisation and are a great humectant.  They have also been found to increase skins barrier function.  A combination of the PHA and low pH makes the topical use of  honey good for all skin types.

Natural Humectant

Natural humectant - Hydrophilic (water loving) properties of honey make it a strong humectant.  As discussed honey has a low water content of around 18.8% however it will absorb water from the atmosphere of a relative humidity of 60%. This ability to draw in water, its hygroscopy can help keep the skin plump and moist.

 Microbes in honey

Although in its pure an natural state honey has many antibacterial properties, it also contains a number of micro organisms that remain  dormant in its undiluted state.  Many micro organisms can not survive in pure honey due to its hyperosmotic nature, which draws moisture away from the microbes, killing them.

Microorganisms that do survive  are those that can withstand the acidity, concentrated sugar, and other antimicrobial characters of honey. These microbes come from various sources - the environment and the bee itself.

''Microorganisms found in honey have been identified). They include bacteria, yeasts and moulds. Most bacteria and other microbes cannot grow or reproduce in honey i.e. they are dormant and this is due to antibacterial activity of honey. Various bacteria have been inoculated into aseptically collected honey held at 20°C. The result showed loss of bacterial viability within 8–24 days. It is only the spore forming microorganisms that can survive in honey at low temperature. The spore count remained the same 4 months after. Bacillus cereus, Clostridium perfringes and Clostridium botulinium spores were inoculated into honey and stored at 25°C. The Clostridium botulinum population did not change over a year at 4°C. At 65°C however, no spore were found after 5 days of storage. ''(White PB,  1996. pp. 301–309)

Honey in cosmetic products

Honey can be used in a variety of ways. You can use it on your face to cleans and exfoliate.  There are also many products on the market that contain pure honey. Lush has a self preserved shampoo and a soap and there are other honey containing creams and balms on the market.  You can also get powdered honey to use in completely dry products like bath bombs, bubble bars and cleansing powders.

Pure honey is water soluble so it can be put in the water phase of your product however it is not wise to dilute too much.  You either need to use very small amounts of honey, supporting it with a preservative, or use it in very high quantities so that it aids preservation of the whole formula.  It has been  observed that honey diltued to 50% supports growth of non- pathogenic (non human diseases forming) bacterial strains but kills the dangerous ones.(Gilliam M, Prest DB, 1987;49:70–75.)  That means that although honey diluted by half may not be harmful to humans it might cause the product to degrade and affect its overall stability.

**Image by Muhammad Mahdi Karim (www.micro2macro.net) Facebook Youtube - Own work, GFDL 1.2, https://commons.wikimedia.org/w/index.php?curid=6699147

Below is a selection of studies and reviews that have been done about honey and its antibacterial properties

Gilliam M, Prest DB. Microbiology of Lanial honey bee(Apis melifera) Jounal of Invertebrate Pathology. 1987;49:70–75. White PB. The normal flora of the bee. Washinton AC: Agricultural research service. US Department of Agriculture; 1996. pp. 301–309

Cutis. 2004 Feb;73(2 Suppl):3-13. The use of polyhydroxy acids (PHAs) in photoaged skin. Grimes PE1, Green BA, Wildnauer RH, Edison BL.

Cutis. 2004 Feb;73(2 Suppl):14-7. A polyhydroxy acid skin care regimen provides antiaging effects comparable to an alpha-hydroxyacid regimen.

Edison BL1, Green BA, Wildnauer RH, Sigler ML.

Antibacterial properties of monofloral honey - http://www.sciencedirect.com/science/article/pii/S0963996916300886

Review Biological properties and therapeutic activities of honey in wound healing: A narrative review and meta-analysis - http://www.sciencedirect.com/science/article/pii/S0965206X15000972

Biological properties and therapeutic activities of honey in wound healing: A narrative review and meta-analysis

Ahmad Oryan, Esmat Alemzadeh, Ali Moshiri

Journal of Tissue Viability. May 2016, Vol. 25, No. 2: 98-118

A systematic review and meta-analysis of dressings used for wound healing: the efficiency of honey compared to silver on burns

Terese Lindberg, Oscar Andersson, Molina Palm, Cecilia Fagerström

Contemporary Nurse. Apr 2016: 1-14

Effect of Tualang honey on the anastomotic wound healing in large bowel anastomosis in rats-A randomized controlled trial

Muhammad Izani Aznan, Omaid Hayat Khan, Allah Obhayo Unar, Sharifah Emilia Tuan Sharif, Amer Hayat Khan,Syed Hassan Syed Abd. Aziz, Andee Dzulkarnaen Zakaria

BMC Complementary and Alternative Medicine. Dec 2015, Vol. 16

Modeling the synergistic antibacterial effects of honey characteristics of different botanical origins from the Sahara Desert of Algeria

Hadda Laallam, Larbi Boughediri, Samia Bissati, Taha Menasria, Mohamed S. Mouzaoui, Soumia Hadjadj, Rokia Hammoudi, Haroun Chenchouni

Frontiers in Microbiology. Nov 2015, Vol. 6

Effects of honey on oral mucositis in patients with head and neck Cancer: A meta-analysis

Hye Kyung Cho, Yeon Min Jeong, Ho Seok Lee, Yeon Ji Lee, Se Hwan Hwang

The Laryngoscope. Sep 2015, Vol. 125, No. 10.1002/lary.v125.9: 2085-2092

Medicinal honey as treatment for skin reactions associated with bone-anchored hearing implant surgery

Erynne A. Faucett, Saranya Reghunathan, Abraham Jacob