Bioactives in cosmetics

Objective: Explore the functions of natural substances in cosmetics.

Key question: For cosmetics, what do we mean by natural?

Cosmetics are products generally intended to cleanse or beautify a person. Some examples include deodorants, shampoos and soaps, hair dyes, toothpaste and make-up.

In the EU, the legal definition of a cosmetic is any substance or mixture intended to be placed in contact with the external parts of the human body (epidermis, hair system, nails, lips and external genital organs) or with the teeth and the mucous membranes of the oral cavity with a view exclusively or mainly to cleaning them, perfuming them, changing their appearance, protecting them, keeping them in good condition or correcting body odours.

History of cosmetics

For thousands of years, humankind has been using cosmetics to enhance beauty and hide advancing age and cosmetics have been part of almost all societies. In ancient Egypt, men and women used make-up to enhance their appearance, scented oils to soften their skin and natural pigments to colour their hair. The eyes were accentuated with black kohl eyeliner and eyeshadows and the lips shimmered with pearlescent lipsticks made with a substance from fishscales.

In China, beauty practices were closely related to social, political and economic standing and this can be seen through the centuries in the fashion and beauty trends of each of the Chinese dynasties. A pleasing appearance was of extreme importance. Trends of the Tang Dynasty, for instance, included application of white powder and rouge, darkening of the eyebrows, lipstick and ornamentation on the forehead and cheeks.

In Indian culture, henna is used as a hair dye and also in mehndi, an art form in which intricate designs are painted on the hands and feet using a paste made from the henna tree giving a semi-permanent, reddish-brown pattern. Applying henna is part of Indian culture associated with religious ceremonies such as marriage.

Through the ages, some make-up and cosmetics have been toxic. Lead based make-up was used in Ancient Rome and China for its skin whitening effects and was very popular in Europe during the Renaissance period. Venetian ceruse or Venetian white was a mixture of water, vinegar and lead and regular users experienced lead poisoning due to constant absorption of lead through the skin.

During the Renaissance, women used eyedrops containing the juice of Atropa belladonna or deadly nightshade berries to dilate the pupils and make the eyes appear more seductive, the word ‘belladonna’ coming from ‘beautiful woman’ in Italian. This plant has history of use as a poison and as a medicine and atropine, a compound naturally occurring in deadly nightshade, is used clinically to dilate the pupils and in some other conditions.

To this day, cosmetics are still manufactured that contain toxic constituents in some parts of the world. Skin lightening products are marketed as treatments for uneven skin tone, acne, age spots and freckles and promise to bleach, brighten, whiten and even the skin. Some of these products contain mercury which reduces the skin’s production of the skin pigment melanin. Mercury is a highly toxic metal.

What do we mean by “natural” cosmetics?

Historically, people turned to the natural world as a source of cosmetics and we still do. There is increasing demand for products that are natural, sustainably and ethically sourced and consumers are increasingly seeking products that they perceive do not negatively impact the environment.

But when looking at cosmetics, what do we mean by natural?

The International Organization for Standardization (ISO) provides ISO 16128, an international standard in natural cosmetics. ISO 16128-1, published in 2016, gives definitions for natural ingredients, derived natural ingredients, organic ingredients and derived organic ingredients.

• Natural ingredients for cosmetics are ingredients obtained from plants, animals, microorganisms or minerals. Ingredients obtained from fossil fuels are excluded from the definition.
• Organic ingredients are natural ingredients originating from organic farming methods or from wild harvesting in compliance with national legislation or International Standards where applicable.
• Derived natural ingredients are cosmetic ingredients of greater than 50% natural origin obtained through defined chemical and/or biological processes with the intention of modifying them chemically.

ISO 16128-2 (2017) offers a framework to determine the natural, natural origin, organic and organic origin content of products based on the ingredient characterization. It describes how to calculate the degree of natural or organic origin of a cosmetic ingredient or cosmetic product as an Index. While ISO 16128 does not address the labelling of products or claims made on labels, products can be found on the market labelled with the natural origin percentage.

Skin cosmetics

The skin is the target of the majority of cosmetics. Cosmetics are used to:

• Make the skin clean and fresh
• Hydrate the skin
• Treat imperfections
• Increase elasticity
• Reduce the signs of ageing
• Create uniform pigmentation
• Add colour (skin, lips, lashes)
• Camouflage imperfections

The skin is a protective layer on our bodies, acting as a barrier to allergens, irritants and pathogens (microorganisms that can cause disease). The outermost layer is a dense network of flattened, dead cells that help keep the skin hydrated by preventing water evaporation. These cells can also absorb water to increase the hydration of the skin.

Vegetable oils and fats can help improve the skin’s barrier function and overall appearance and texture and natural products such as cocoa butter, jojoba oil, argan oil, almond oil to name but a few are incorporated into moisturisers, lotions and ointments or used as oils. Waxes such as beeswax and carnauba wax are used in lipsticks. Gel formulations are also cooling, soothing and hydrating and products such as aloe vera gel can help relieve sunburn.

Natural products are a source of fragrances and pigment colours for make-up. Essential oils, such as lavender, rose, jasmine, neroli are highly valued as natural fragrances for cosmetics. Annatto, an orange red pigment derived from the seeds of the achiote tree, the deep lavender blue pigment of butterfly pea flowers, beetroot, and saffron are all sources of colours.

As we age, and hormone levels change, the skin becomes thinner, it loses collagen and elastin and undergoes some changes influenced by certain external and internal factors. The changes in the skin are one of the most obvious signs of ageing and include:

*Thinning *Sagging skin *Wrinkles *Dryness *Age spots *Loss of fat and loss of natural smoothness of the skin

Many of these ageing effects are promoted by free radicals (unstable atoms or molecules created during metabolism that can damage the body) and antioxidants are included in cosmetics to combat this damage and slow these processes. Plant extracts are included in cosmetics for their antioxidant effects and these extracts often overlap with the phytonutrient containing foods that we see as healthy e.g. green tea, grape seed.

Vitamins are often included as individual formulation ingredients such as vitamin C and vitamin E and individual phytochemicals are often used too. Chemicals produced by plants can affect the process of melanin production in the skin and are included in cosmetic formulations to treat skin hyperpigmentations and to even the skin tone. Liquorice comes from Glycyrrhiza glabra and the extract of this flowering plant is included in cosmetics for its anti-ageing and anti-inflammatory properties.

Liquorice extract contains compounds which help control the production of melanin pigment in our skin.

Many other natural products have this skin lightening effect which is harnessed in cosmetics to address age spots and other uneven pigmentations. Arbutin, a compound in the bearberry plant, and kojic acid, a compound produced by species of fungi, are two further natural products formulated in cosmetics for hyperpigmentation.