Classification of Cosmetics and Cosmeceuticals

The study of cosmetics is called "Cosmetology". It is the treatment of skin, hair, nails and includes manicure, pedicure, applying of artificial nails on a special occasion, hair styling, shampooing hair, body hair removal, chemical hair relaxers or straighteners, perming, coloring, highlighting of hair, hair extensions and wig treatments. A person who is licensed in cosmetology is called Cosmetologist. Products covered under cosmetics range from hair care, oral care, skin care, lipsticks, nail polishes, extenders, deodorants, body powder and aerosols to quasi-pharmaceutical over-the-counter products such as antiperspirants, dandruff shampoos, antimicrobial soaps, anti-acne and sunscreen products.  

Table below classifies the cosmetics based on the site of application and presents the products in each category.

Types of Cosmetics

Facial cosmetics

Hair cosmetics

Eye Cosmetics

Dental and Oral Cavity


Antiperspirants & deodorants

Miscellaneous Cosmetics

Cleansing preparations

Hair dye

Eye liners

Tooth paste

Antiperspirants: Liquid


Stuck Powders

Blackhead removers

Skin nourishing (sunburn, sunscreen)

Hair oil

Eye gloves

Mouth washes

Deodorants: Powder Liquid Cream Sticks

Toilet soaps

Skin tonic

Hair creams


Teeth whitening, Chewing gum


Anti-stress marks removers

Shaving cream

Hair gels

Eye brow pencils

Tooth powder



Make up: Vanishing cream, Powders, Face mark removal, Multipurpose


Antidandruff preparations

Contact lens





Hair removing creams






Shampoos: Clear liquid Liquid cream Solid cream Egg/herbal/oil Dry powder  






Cosmetics are derived from both synthetic and natural sources from ancient times. As on now we have mostly synthetically derived products. However, naturally, derived products are still competitive with the latest chemically manufactured items because of the safety they offer.

Designing of modern cosmetics is based on biological data that has improved cosmeceuticals for antiageing, hair growth, and skin care. Demand for the cosmetic designer in the above sectors is increasing day by day. FDA and other organizations prefer the utilization of natural cosmetics developed with the help of plant tissue/cell culture technology.

Herbal Cosmetics
The history of herbals is really the history of humankind, for every culture throughout time has relied upon herbs for its medicines and cosmetics. Some cultures for instance, India and China have maintained a strong, unbroken tradition of herbalism for several centuries, while in Europe and North America its popularity has soared and plunged periodically as Western medicine and cosmetics achieved greater prominence. 

Today, however, interest in herbal products has increased once again, with an appreciation of its safer, holistic approach. Probably the first system of herbal products, apart from the almost instinctive use of plants
for healing that existed from the dawn of history and is still practiced by remote tribes, was developed in India well over 4,000 years ago. 

From India, the use of plants probably travelled with migrating people into China. Traditional Chinese medicine has developed a strong philosophical viewpoint on health and disease, with treatments ranging from herbal medicines to acupuncture, moxibustion and massage techniques. Moxibustion is a traditional Chinese medicine therapy which consists of burning dried mugwort (Artemisia argyl) on particular points on the body. It plays an important role in the traditional medical systems of China, Japan, Korea, Vietnam, and Mongolia.

Ancient scriptures like Abhijnana, Shakuntalam and Meghadootam of Kalidasa and many mythological epics encompass the reference of cosmetics like: Tilak, Kajal, Alita and Agaru (Aquilaria agalbeha) that were used as body decorative and to create beauty spots on the chin and cheeks in the era ruled by gods and their deities. In fact, the concept of beauty and cosmetics is as old as mankind and civilization. The famous depictions in the Ajanta and Ellora caves, Khajuraho prove that not only women but men also adorned themselves with jewels and cosmetics. Encrypted in history is the Aryan period that witnessed the use of turmeric- haridra (Curcuma Longo, Linn), saffron, alkanet, agaru, chlorophyll green from nettle plants and indigo for bodily-decorations apart from using raktachandan (Pterocarpus santalinus Linn), Chandan (Santalum album) for beautification.  Using mehendi (henna) for dyeing hair in different colors and conditioning was also practiced in the olden times.

Nutracosmetics are an emerging class of health and beauty aid products that combine the benefits of nutracosmetical ingredients with the elegance, skin feel, and delivery systems of cosmetics. Herbs and spices have been used in maintaining and enhancing human beauty because herbs have many beneficial properties, such as sunscreen, anti-aging, moisturizing, anti-oxidant, anti-cellulite, and anti-microbial effects. As compared to synthetic cosmetic products, herbal products are mild, biodegradable, and have low toxicity profile. 

Numerous chemical toxins, micro-organisms, chemicals, infections present in atmosphere cause damage to skin. Cosmetics alone are not sufficient to take care of skin and body parts; they require association of active ingredients to check the damage and ageing of the skin. Herbal cosmetics have now emerged as the appropriate solution to the current problem. Personal care industry is currently more concentrated on herbal cosmetics, as now-a-days it is a fast growing segment with a vast scope of manifold expansion in coming years.

Herbal cosmetics represent cosmetics associated with active bio-ingredients, nutraceuticals or pharmaceuticals. The use of bioactive phytochemicals from a variety of botanicals has dual functions: 
  1. These serve as cosmetics for the care of body and its parts,
  2. The phytoconstituents present therein influence the biological functions of skin and provide nutrients necessary for the healthy skin or hair. 

In general, botanicals provide different vitamins, antioxidants, various oils, essential oils, hydrocolloids, proteins, terpenoids and other bioactive molecules. Necessary efforts are required to associate the modern cosmetology with bioactive ingredients based on the traditional system of medicine leading to emergence of novel cosmeceuticals for skin and body care.

Ideal Properties of Cosmetics
Cosmetics are intended to be applied/ placed in contact with external parts of human body namely, skin, hairs, nails, lips, teeth, and mucous membranes of the oral cavity. Considering the fact that these preparations are in contact with the said parts for considerable duration of time, following are the desirable characteristics of cosmetics.
  1. Cosmetics should be non-toxic, non-irritant and acceptable to regulatory agencies.
  2. They should be readily applicable and pleasant in use.
  3. They should be physically and chemically inert.
  4. They should be Economical.
  5. They should have long-lasting property.
  6. They should have the ability of masking the imperfections of the skin.
  7. They should be stable and have a good appearance.
  8. Cosmetics should provide significant cleaning if intended for.
  9. They should be easily removed from the skin when needed.

Classification of Cosmetics
Cosmetics are classified into four main categories which are as follows:
  1. According to their use.
  2. According to their functions.
  3. According to their physical nature.
  4. According to their state.

A. Classification of Cosmetics according to their use:
Based on the site of application, cosmetics are classified into main five categories.
  1. Use for skin.
  2. Use for nails.
  3. Use for teeth and Mouth.
  4. Use for Hairs.
  5. Use for eyes.

For skin: 
The skin mainly intends to protect human beings against environmental aggressions. The cosmetic products that are poured, rubbed or applied on the skin are known as skin cosmetics. Skin cosmetics are the range of products that support skin integrity including nutrition, avoidance of excessive sun exposure, and appropriate use of emollients that enhance skin tone and beautification. These are also components of wound healing, neonates, elderly, stomas, radiation treatment and with some medication. 

Examples are creams, powders, deodorants, lotions, antiperspirants, moisturizers, perfumes, skin toner, etc.

For nails:
The nails, in particular the nails plates of the fingers of hands and feet, have been subjects of decoration in terms of shine or colour. The products used include nail lacquers, nail lacquer remover, cuticle removers, manicure and pedicure preparations.

For teeth and mouth:
Dental care products are meant for keeping the dental structure healthy, strong and protected against any infection (oral). These are also meant for keeping the enamel on teeth intact. Cosmetic mouthwashes consisting of water, alcohol, flavour (essential oils) and colour primarily function to remove or destroy the bacteria in the oral cavity. 

Examples are dentrifices, mouthwashes, dental powders, lotions, gargles, mouth fresheners.

For eyes:
Since eyes are very sensitive and important part of our body and also require high lightening during beautification but with utmost care and protection.

Examples are eye creams, eyelashes, eyeliners, mascara and eye shadow.

For hairs:
Hair cosmetics are the range of products that are used for hygiene of hairs involving hairs grows from human scalp, facial, pubic and other body hairs. Hair care routines differ according to an individual's culture and the physical characteristics of one's hair. Hairs may be coloured, trimmed, shaved, plugged or otherwise removed with treatments such as waxing, threading etc. The hair care products include shampoo, hair removers, hair dyes, hair sprays, depilatories, hair wave preparation, epilatories, shaving preparation etc.

B. Classification of cosmetics according to their functions

Curative and therapeutic:
Some cosmetic products which are used for the purpose of beautification are also meant to have curative and therapeutic property.
e.g. antiperspirants and hair preparations.

Some cosmetic products have the protective functions which not only protect our skin from external environmental factors, but also reduce its intensity so as to enable the skin to develop its own protection against exposure. e.g sunscreens.

The cosmetic products which are applied to correct or improve tone and mask the imperfection either from face, hairs, heals, nails, teeth etc. e.g. Crack creams.

Decorative function of the cosmetics gives the person a feeling of confidence, happiness during occasion. The cosmetic product which provides decorative function highlights different body parts like nail and hairs by different shades of colours and shine etc. e.g. lipsticks, nail lacquer, eyelashes, mascara etc.

C. Classification of cosmetics according to their physical nature

Aerosols are pressurized dosage forms containing one or more active ingredients. In aerosols, the product material can be removed without contamination of remaining materials, so that the product can be delivered directly to affected area.
E.g. Hair perfumes, after shave lotion, etc.

Cakes are the semi-solid preparations which are formed by applying accurate pressure. A well formulated cake will come out easily with a sponge and should cover the skin uniformly. E.g. Rouge compact, makeup compact.

An emulsion is a biphasic liquid dosage form in which two immiscible liquids are made miscible by the addition of a third substance known as emulgent or emulsifying agent. The cosmetic products covered under this category include vanishing cream, cold cream, cleansing cream, all purpose cream.

An oil is any neutral, non-polar chemical substance, that is a viscous liquid at ambient temperature and is both hydrophobic and lipophilic. Oils may be of animal, vegetable or petrochemical origin. They may be volatile or non-volatile. E.g. Hair oil.

These are semisolid preparations meant for external application to the skin. Due to the presence of large amounts of solids, they are less attractive cosmetically than ointments. Since pastes are stiff, they do not melt at ordinary temperature, thus forming and holding a protective coating over the areas to which they are applied.
e.g. Tooth paste, deodorant paste.

Powders are the solid dosage forms which are meant for internal and external use. They are available in crystalline or amorphous form. In cosmetics, powders are used for face and body care, not only by women but also by men. The body powders are also known as dusting powders. e.g. tooth powder, talcum powder, face powder.

Solution is a homogeneous mixture composed of two or more substances. The solution assumes characteristics of solvent i.e. its phase. e.g. after shave lotions, hand lotions, astringent lotions, etc.

Soap is a salt of fatty acids. Soaps are used for cleaning and are obtained by treating vegetable or animal oils and fats with a strong base such as sodium hydroxide and potassium hydroxide in aqueous solution. e.g. shaving soaps, bathing soaps, toilet soaps and shampoo soaps.

e.g. lipsticks, deodorant sticks.

D. Classification of cosmetics according to their state

Solid: e.g. Powders.
Liquid: e.g. Lotion, mouthwashes.
Semisolid: e.g. gel, cream.

Cosmetic science is a fast moving area. Furthermore, rapid and extensive changes in the worldwide regulatory context of cosmetics, increasing constraints and limitations in the choice of cosmetic ingredients and regular pressure from the media force the cosmetics formulator to think differently about his products. According to USFDA, the definition of cosmetic and drug is clear and simple. However, there is one legal parameter which thoroughly confounds the issue, that cosmetic must "not affect structure and function of skin." 

This statutory differentiation of drugs from cosmetics was probably appropriate for the state of knowledge when the USFDA rules were written, more than a half century ago. Since then there has been tremendous increase in knowledge of the physiology of skin has brought the law and biology into conflict. The truth is that all topical substances, whether as simple as water or as complex as multi-ingredient moisturizers, inevitably will affect the structure and function of skin. No topical product is completely inert. 

In 1938, the ideas regarding skin physiology were primitive. Now it is known that skin exposed to water for 48 hours demonstrates cytokine release, producing a condition known as hydration dermatitis. Under electron microscopy, water can produce changes in Langerhans cell and mast cell
function. Hydration dermatitis is a disease, but water is not a drug. Since everything applied to the skin produces change, so there is need of third category of products known as cosmeceuticals. The concept of cosmeceuticals is comparatively new in India and not much rules and regulations exist to abide by them. Conceptually, they fall under grey area of conventional drugs and cosmetics. In most countries, a suitable regulatory category for these hybrid products does not exist and therefore most complications in market development arise from a lack of a clear definition and the consequent legal framework for cosmeceuticals.

Some cosmeceuticals are naturally-derived while others are synthetic; but all contain functional ingredients with either therapeutic, disease fighting, or healing properties.

Mechanism of Action of Cosmeceuticals
Cosmeceuticals improve appearance, but they do so by delivering nutrients necessary for healthy skin. The cosmeceutical products act functionally. Evidence to support the claims or use of cosmeceutical ingredients are often lacking in literature. Many contain biologically active ingredients, and in general, cosmeceuticals undergo tests to determine safety, but claims of efficacy are largely unsubstantiated. Efforts have only recently been initiated to address the issues surrounding quality control and to establish industry standards and regulations. Demonstrating the skin effect of a cosmeceutical can be difficult; there are no placebos because anything that is applied to the skin will have an effect. However, ten basic mechanisms of action of cosmeceuticals are enlisted in the Table below.

Ten basic mechanisms of action of cosmeceuticals



Mechanism of Action

Example of Cosmeceutical


Activate a receptor

Retinoids: Tretinoin, Retinol


Enhance barrier function

Moisturizers     based  on Petrolatum, Silicone, Mineral oil, Glycerin


Increase exfoliation

Salicylic acid


Normalize cellular repair

Copper peptides


Decrease inflammation

Green tea


Inhibit oxidation

Lactobionic acid, Vitamin E


Provide a cellular messenger



Regulate cellular communication



Modulate pigmentation

Avobenzone, micronized titanium dioxide


Deliver photo protection

Avobenzone, micronized titanium dioxide and microfine zinc oxide

Classification of Cosmeceutical Products
Cosmeceuticals are divided into eight categories as shown in Figure below.

1. Retinoids
Retinoids are premier evidence-based cosmeceuticals, as they function through surface-cell receptor interaction to produce a clinically defined effect. Other retinoids such as pro-8 vitamins (niacinamide and panthenol) function differently by physically enhancing the barrier properties of the stratum corneum. These are the most prevalent cosmeceuticals in the market.

They consist of natural and synthetic derivatives of vitamin A that reduce hyperpigmentation and inhibit enzymes from breaking down collagen. Many of their cosmeceutical claims are based on data derived from studies on tretinoin and other classes of retinoid drugs. Some key retinoids include retinoic acid (tretinoin), retinol, and retinaldehyde.

Retinoic Acid (Tretinoin): 
There is extensive literature on the use of tretinoin, which is considered to be one of the most potent compounds for treating the signs of aging and/or photodamaged skin, including fine lines, hyperpigmented spots, and wrinkles. However, side effects such as burning and scaling have limited its acceptance. In order to minimize these side effects, various novel drug delivery systems are being developed.

Retinal (Vitamin A): 
Retinol is oxidized into retinaldehyde and then into retinoic acid, the bi. a biologically active form of vitamin A. In vivo studies showed that topical retinol had only a modest retinoid-like biological activity compared with topical retinaldehyde and retinoic acid. Two randomized, controlled trials reported significant improvement in fine wrinkles after 12 and 24 weeks of treatment, respectively.

Retinaldehyde is viewed in a large part as an intermediate form during the conversion of retinol to retinoic acid. Studies have shown that it does have activity in human skin. Moreover, some studies have reported that this retinoid can produce significant clinical improvement in the appearance of fine and deep wrinkles.

2. Sunscreens
Sunscreens are the single most important cosmeceutical because they protect the skin against solar radiation, which is the most important damaging environmental agent. As a result, they help to prevent the signs of aging. To be effective, sunscreens should provide broad spectrum coverage that includes both UVA and UVB blocking agents to inhibit photoaging and be part of a daily skin care regimen. UVA and UVB radiation contribute to the disruption of the extracellular matrix, a vital phenomenon related of photoaging.

Broadspectrum UVA and UVB sunscreens are the cornerstones of photoaging therapy. Sunscreens contain active ingredients that act as ultraviolet filters. Enzophenones (dioxybenzone, oxybenzone, sulisobenzone) give protection in the UVB and UVA II range (320-340 nm). The recommended application is 2mg/cm2, though this is rarely achieved in real-life practice.

Green Tea Extract: 
Research has shown that green tea (Camellia sinensis) polyphenols are potent suppressors of carcinogenic activity from UV radiation and can exert broad protection against other UV-mediated responses, such as sunburn, immunosuppression, and photoaging.

Ferulic Acid: 
This compound, derived from plants, is considered to be a potent antioxidant and has been shown to provide photoprotection to skin. Furthermore, when ferulic acid is combined with vitamins C and E, the product has been shown to provide substantial UV protection for human skin. Moreover, because its mechanism of action is different from sunscreens, ferulic acid could be expected to supplement the sun protection provided by sunscreens.

3. Moisturizers
Moisturizers are the most useful product for the management of various skin conditions (e.g., atopic dermatitis, psoriasis, pruritus, and aging skin). These products include emollients, occlusives, and humectants. The majority of moisturizers enhance skin barrier function. Moisturizers claim to make the skin smoother, softer, more radiant, less wrinkled, and firmer.

They improve the tactile properties of dry and aging skin, restore the normal barrier function of the skin, and reduce the release of inflammatory cytokines. Moisturizers based on materials such as petrolatum, silicon, mineral oil and glycerin enhance skin barrier functions. Moisturizers restore water content to the epidermis and provide a soothing protective film.

4. Antioxidants
Topically applied antioxidants enhance the skin's natural antioxidant protection system. They reduce free-radical damage by blocking the oxidative processes in cells. These are used to protect skin from photodamage, cancer and photoaging. Antioxidants inhibit inflammation that causes collagen depletion. They protect against photodamage and skin cancer. However, there is no completely satisfactory agent available for humans. Explanations for this could include the fact that:
  • Reactive oxygen species (ROS) affect different pathways in different situations and an antioxidant focused on one such pathway may be ineffective in a redundant pathway.
  • ROS pharmacokinetics in the target tissue may not relate to that of the antioxidant.
  • Bioavailability and target organ concentration of the antioxidant may be a limiting issue.
Common antioxidants include alpha-lipoic acid (ALA), L-ascorbic acid (vitamin C), niacinamide (vitamin B3), N-acetyl-glucosamine (NAG), a-tocopherol, and ubiquinone (CoQ10) that are described below.

Alpha-Lipoic Acid (ALA):
Alpha-lipoic acid has anti-inflammatory properties and acts as an exfoliant. In a split face study, topical 5% ALA applied b.i.d. for 12 weeks reduced skin roughness, lentigines and fine wrinkles. This agent does not protect against UV-induced erythema or reduce the number of sunburn cells.

L-Ascorbic Acid (Vitamin C):
There is clinical data to support the use of topical vitamin C to improve fine lines and reduce both pigmentation and inflammation, and many cosmeceutical formulations contain this antioxidant. However, many of these formulations are not effective on the skin because:
  • The concentration of L-ascorbic acid is too low.
  • Exposure of the product to air and light compromises its stability of the product.
  • The L-ascorbic acid molecule (in the form of an ester or a mixture of isomers) cannot be absorbed or metabolized effectively by the skin.

In high enough concentrations (i.e., at least 10%) of the non-esterified, optimal isomer, this antioxidant does inhibit UV damage. It is important to note that stabilizing ascorbic acid presents many formulary challenges. However, a formulation that has an acid pH of approximately 3, may optimize vitamin C absorption. Newer formulations of stabilized ascorbic acid derivatives may prove to be more efficacious.

Niacinamide (Vitamin 83):
Niacinamide is a potent antioxidant that is generally well tolerated. It improves the lipid barrier component of the epidermis, thus reducing transepidermal water loss, and acts as an inhibitor of melanosome transfer, resulting in reduced hyperpigmentation. Studies have revealed a significant reduction in fine lines and wrinkles, hyperpigmented spots, red blotchiness, and skin sallowness, as well as improved skin elasticity.

N-Acetyl-Glucosamine (NAG):
NAG is a more stable form of glucosamine and may prevent new signs of photodamage from occurring and fade existing imperfections by interrupting the chemical signals that promote melanin production. A placebo-controlled study comparing 3.5% NAG with the combination of 3.5% NAG plus 3.5% niacinamide on hyperpigmented spots showed a superior reduction in pigmentation in the combination treatment group versus both the placebo and NAG-only groups. When combined, they produce synergistic effects.

Alpha-Tocopherol (Vitamin E):
When taken orally, cx-tocopherol protects membrane lipids from peroxidation. It has been shown to reduce sunburn cells after UV exposure, neutralize free radicals, and act as a humectant. Its activity can be renewed by combining it with a vitamin C preparation. As a component in topical formulations, it, like unmodified L-ascorbic acid, has shown some limited efficacy. However, when a stable formulation delivers a high concentration of the non-esterified, optimal isomer of this antioxidant, vitamin E does inhibit the acute UV damage of erythema, sunburn, and tanning, as well as chronic UV photoaging and skin cancer. Because vitamin C regenerates oxidized vitamin E, the combination in a cosmeceutical formulation is synergistic - particularly with regard to UV protection.

Ubiquinone (CoQ10):
Ubiquinone is a naturally occurring, fat-soluble antioxidant and there is good in vitro evidence that it can suppress fibroblast production of UVA-induced collagenase, thereby reducing collagen breakdown. It has been shown to be effective against UVA-mediated oxidative stress in human keratinocytes. Ubiquinone was also able to significantly suppress the expression of collagenase in human dermal fibroblasts following UVA irradiation. Another study showed that ubiquinone can strongly inhibit oxidative stress in the skin induced by UVB. It is an effective antioxidant protecting the dermal matrix from both intrinsic and extrinsic aging.

Grape Seed Extract It is a potent antioxidant and has been shown to speed wound contraction and closure. The topical application of grape seed extract has also been shown to enhance the sun protection factor in humans.

E. Hydroxyacids
These include cx-hydroxy acids (AHAs; glycolic acid, lactic acid) and β-hydroxyacids (BHAs; salicylic acid). Hydroxyacids are used worldwide and most probably for centuries as active dermatological drugs and cosmetic ingredients. The exact mechanism of action of hydroxy acids remains unknown and is largely controversial. Some experts claim that AHAs increase the synthesis of glycosaminoglycans which improve the quality of elastic fibers, and increase the density of collagen; whereas BHAs have dermolytic properties and help in various xerotic and ichthyotic disorders. 

AHAs are also referred to as fruit acids; and are a common ingredient of cosmeceutical products. Examples include citric acid, malic acid, glycolic acids, pyruvic acid, lactic acid, and tartaric acid. AHAs improve skin texture and reduce the signs of aging by promoting cell shedding in the outer layers of the epidermis and by restoring hydration. The mechanism of action is not completely understood. One hypothesis suggests that AHAs reduce the calcium ion concentration in the epidermis and, through chelation, remove the ions from the cell adhesions, which are thereby disrupted, resulting in desquamation. This is enhanced by cleavage of the endogenous stratum corneum chymotryptic enzyme on the cadherins, which are otherwise protected from proteolysis by conjugation with calcium ions. The resulting reduction of the calcium ion levels tends to promote cell growth and slow cell differentiation, thus giving rise to younger-looking skin.

F. Topical Proteins and Peptides
Cosmeceutical peptides have the potential to improve the appearance of aging skin. Topical peptides are regarded as cellular messengers that are formed from amino acids and are designed to mimic peptide fragments with endogenous biologic activity. These pentapeptides (e.g., KTTKS) are comprised of a subfragment of type I collagen propeptide, and play a role in signaling fibroblasts to produce collagen in the skin, which can improve the appearance of wrinkles. One variation, the palmitoyl pentapeptide known as Pal-KKTKS (Matrixyl™, Sederma) was tested in a controlled, double-blind, left-right randomized, split face study of 93 women between 35 and 55 years of age who had Fitzpatrick I-ill type skin.

Pal-KTTKS concentration was 3 ppm; both groups were treated twice daily for 12 weeks. Improvements in wrinkle appearance and length were observed. There are various types of cosmeceutical peptides such as signal peptides, carrier peptides, and neurotransmitter-inhibiting peptides. Overall cosmeceutical peptides trigger a wound-healing mechanism that activates fibroblasts in response to fragmented chains of elastin and collagen. Peptides increase collagen production to improve skin appearance, resulting in smoother skin.

G. Depigmentation agents
Skin-lightening agents added to product formulations have become increasingly popular. Common depigmenting ingredients include hydroquinone, ascorbic acid (vitamin C), kojic acid, and licorice extract (glabridin).

Hydroquinone has been the agent of choice for skin lightening. However, there are concerns over exogenous ochronosis and permanent depigmentation, as well as possible carcinogenicity, and it has been banned as an over-the-counter depigmenting agent in Europe, Australia and Japan. The US FDA has proposed concentrations between 1.5% and 2% in skin lighteners. A recent report suggested that this concern has been based mainly on studies with animal models utilizing long-term exposure at high dosages. Routine topical application may pose no greater risk than that from levels present in common foods.

Hydroquinone is effective and widely used for the treatment of melasma, and post-inflammatory hyperpigmentation. It acts by inhibiting the conversion of tyrosine to melanin.

Ascorbic acid (Vitamin C):
Ascorbic acid is a naturally occurring antioxidant found in citrus fruits and leafy green vegetables. It is hydrophilic, so skin penetration is low.

Kojic acid:
Kojic acid is a less commonly used bleaching agent. When combined with di-palmitate, there is improved skin penetration and greater stability, but there is little research to support its efficacy.

Licorice Extract (Glabridin):
Several studies on melasma have shown good efficacy with only mild irritation that disappeared with discontinuation.

H. Growth factors
Epidermal growth factor (EGF) stimulates epidermal growth and is used in the treatment of burns and excision wounds, where it accelerates re-epithelization. Transforming growth factor (TGF) stimulates normal skin growth and cellular growth and repair. TGF exerts positive regulatory effects on the accumulation of the body's extracellular matrix proteins.

TGF is also a mediator of fibrosis (repair tissue formation) and angiogenesis (development of new blood cells) and it promotes the healing of wounds.

Formulation Considerations
Although some products claim for the active ingredients used in cosmeceutical formulations are evidence-based, consumers often place their confidence in the claims made by the manufacturer. Without testing to assess the efficacy of key active ingredients in relation to overall product content, it is possible that at inadequate concentrations, any beneficial effect will become unapparent. Ensuring consistency of formulations is also an area that has been neglected and necessitates regulation.

One of the most important parts of any cosmeceutical is the vehicle that carries the active ingredient into the skin. Vehicle delivery systems can:
  • Augment the efficacy of the active ingredient
  • Inactivate the active ingredient
  • Improve the skin barrier
  • Provoke allergic contact dermatitis.

In some skin conditions, the vehicle may be as good as the active preparation, and it may take three months or more to see a difference.

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