Is Vitamin K prohibited in cosmetic products?

The vitamin K is a group of fat-soluble vitamins that play a role in blood clotting. There are different forms of vitamin K that belong to the quinone family. What differentiates them is the nature of the carbon chain attached to the quinone.

• Vitamin K1 : Also known as phylloquinone, phytomenadione, or phytonadione, it is naturally synthesised by plants. It can be found in photosynthetic organisms such as algae, for example.

• Vitamin K2: Also known as menaquinone, it is found in the bacteria of the intestinal flora and is derived from the plants we consume.

• Vitamin K3 : Also known as menadione, it is one of the synthetic forms of vitamin K. However, due to its side effects on the liver, it is not used in human nutrition.

However, according to the European Commission Directive 2009/6/EC of 4th February 2009, and following consultation with the Scientific Committee on Consumer Products (SCCP), it was decreed that the use of pure vitamin K1 in cosmetics is not safe, due to risks of skin allergies and other negative impacts. Consequently, its use is now prohibited in Europe.

Indeed, several cases of skin reactions have been recorded following the topical application of Vitamin K1. The estimated frequency was 2.5 to 4 skin intolerances per 100,000 cosmetic products sold at a concentration between 1 and 2%. It is particularly known to cause the onset of allergic contact dermatitis.

Furthermore, Vitamin K1 possesses a sensitisation potential, meaning that its topical application can lead to significant sensitisation to Vitamin K1, which is used in treatments for blood clotting. This sensitisation can therefore prove concerning for patients undergoing treatments based on this fat-soluble vitamin.

Therefore, Vitamin K1 would act as an allergen.

These observed reactions may be due to the activation of the immune system. When a person sensitive to Vitamin K1 comes into contact with this substance, their immune system may overreact, mistakenly identifying Vitamin K1 as a threat. This triggers the release of inflammatory mediators, such as histamines, which cause skin allergy symptoms such as redness, itching, and rashes.

Finally, it appears that vitamin K1 may be photo-unstable. Indeed, a study conducted by Vincent KAM-WAI WONG and Paul CHI-LUI HO demonstrated that when exposed to UV light at 254 nm, vitamin K1 rapidly decomposed with a degradation rate constant of 7.63 per day-1. This situation could potentially compromise the stability of the formula in which it is included and could potentially be photosensitising for the skin, making it vulnerable to free radicals produced by oxidative stress.

Currently, cosmetic products claiming the presence of vitamin K typically contain the oxidised form (vitamin K oxide), which is less irritating and more stable. Moreover, reactions are individual and will depend on the person's allergic situation.