Hair and scalp are the body areas most exposed to the environment—sunrays, pollution, dry and humid air—and mechanical stress and occlusion—combing, hats, head protections and helmets—to chemical and physical stress—perms, styling, dyeing. Indeed, they have many different physico-chemical and biological characteristics.
First of these is reduced air circulation and hindered oxygen exchange on the scalp surface, which can bring localized high concentrations of carbon dioxide. Second are the capillary forces that facilitate the diffusion of sebum along the hair shaft and its spreading onto nearby hair by physical contact. This lipid layer protects the hair and scalp, but it also can trap powders, dissolved chemicals and other contaminants that are suspended in the air. Additionally, the bacterial and yeast proliferation on the scalp is commonly associated with enhanced desquamation, itching, scratching and redness, all of which are frequent manifestations of scalp disequilibrium. These states impact the appearance and the perceivable health of hair.
Neither women nor men want unattractive hair or an uncomfortable scalp. Most demand their hair and scalp to be in pristine condition, as their appearance is critical for easy social communication, sexual attraction, personal identity and style elements. Counteracting the evidence of age damages to the hair is also a growing concern, as the diameter, mechanical properties and tactile perception—fineness, roughness, slipperiness—of human hair become progressively worse as time goes by.1
Hair and scalp care and maintenance are among the key tasks of many cosmetic formulae. Their functions satisfy the complex needs of this body district: cleansing, nourishing, protecting, stimulating, conditioning, and enhancing appearance. Besides hair styling and coloring, scalp health is the primary requirement for pleasant and satisfactory hair appearance. Indeed, all nutrients brought by the blood flow through microcirculation to the hair root participate in the proper growth of the hair shaft. In other words, scalp care and hair care are strictly bound, at least in a first instance.
Hair maintenance, protection and strengthening are applied to the hair for long periods after the initial phase of formation of the hair shafts inside the scalp. After its rise from the scalp surface, the hair structure cannot proliferate further or improve; it only progressively decays. Nevertheless, the hair porosity, its superficial activity and controlled swelling potential; the slow, in-depth diffusion potential of small molecules inside the hair fiber; the variable electrostatic behavior, the surface discontinuity, the protein (keratin) structure, the variable water content and the pH-sensitive behavior of hair all leave enough space for the local application of many functional substances, after adequate cleansing procedures.
New Scalp and Hair treatment strategies
Scalp and hair cleansing: a non-simple task. The hygiene operation applied to hair and scalp is many-sided: removing undesired materials coating the hair and scalp surface, physiological and environmental odor elimination, detaching dead, horny layer cells and dissolving oxidized sebum lipids; reducing bacterial and mycotic flora and eliminating all materials derived from environmental pollution. All these functions should be carried out without heavily influencing the scalp homeostasis.
Today’s opinion is that skin is like an endangered environment: its cleansing must take place while respecting the scalp and hair equilibrium, from the chemical, physiological and microbial points of view.
Modern cleansing strategy implies a “gentle cleansing” philosophy and the adoption of “macro” surfactants. Innovative formulae should respect scalp and hair lipids as they perform many protective functions. We are in an age of “active” surfactants, molecules with special functionality that are more frequently encountered in skin care products. In other words, as we wash repeatedly during the day and our lipids fund is heavily endangered, new cleansing molecules should preferentially perform some type of skin treatment more than skin cleansing.
Foaming vegetal extracts contain macro surfactants, which for their bulky dimensions cannot penetrate deep into the skin are being proposed. Moreover, new cleansing formulae contain new polymers, which boost skin adhesion and improve the actives efficacy in rinse-off products. By their substantivity to the skin, these polymers act as a reservoir of antioxidant, anti-inflammatory and anti free-radical actives. In the long term, they promote skin homeostasis and cell renewal.
2) Dry oils
These are blends with light-feel emollients, containing lipo-soluble actives (vitamins E and A, plant extracts, active principles). They provide restoration of the lipid film on the skin surface. Some lipids, like vegetal oils, squalene and hydrogenated polydecenes, help the recovery of lipid membrane equilibrium. With the supplementation of ω3-ω6 fatty acids and the rich unsaponifiable fraction contained in some vegetal oils, the stabilization of cells lipid membrane is easily obtained.
Specific synthetic lipids, like isostearyl isostearate, are reported to stimulate aquaporin-3, which regulates water exchanges at the level of cell membranes. Oils sometimes show short-term occlusive properties with marked effects on lipid membranes and TEWL reduction. But what is more interesting is their water compartmentation power, which gives long-lasting stabilizing structuration to the water content of skin cells and structures. The question is if the extended use of oil materials might damage lipid membranes has a reasonably negative answer, because the high molecular weight oils generally used have scarce solvent effect.
Indeed, some categories of oils should not be used, depending on specific criteria of purity, concentration in formula, physico-chemical characteristics like polarity and sensorial items like color and odor. Even if strongly preferred by ‘green’ consumers, vegetable oils can pose formulation problems concerning their purity (heavy metals and pesticides content) and oxidation stability. Their use in a formula requires a proper antioxidant strategy and stringent purity criteria.
On the other side, the excessive use of non-blended mineral oils implies scalp occlusivity and low biocompatibility, as they are generally considered scarcely skin friendly. The best formulation strategy to optimize stability requirements with skin restitution properties is to mix mineral oils (or hydrogenated poly-decenes or poly-isobutenes) with suitable amounts of different polar oils, in order to obtain an equilibrated emollient feel, dry skin relief and replenishment of skin lipids. Additional advantages of oil blends are the low or no need of bactericides and the respect of cutaneous barrier and environment. Their use as cleansers is not accompanied by residue of surfactants onto the scalp and hair surface; therefore they are also advisable for sensitive-and dry skin.
Functional cleansing and scalp repair
In order to obtain long-lasting functionality, ingredients in formulae should have hair and scalp adhesion properties. Hydroxypropyl methylcellulose, micro-emulsions of silicone polymers and quaternized polymers are example of film formers, while poly-saccharides like hyaluronic acid and tamarindus indica seed polysaccharide provide efficient moisturizing & elasticizing effects. Sferulites (solid lipid micro-particles) provide adhesion and work as penetration boosters of active principles.
From opuntia ficus indica,2 new poly saccharides with adhesion promotion properties are obtained. This extract also has wound-healing properties; antioxidant and anti-inflammatory extract from zanthoxylum bungeanum fruit3 have demonstrated lenitive and soothing properties in scalp-care systems. Bakuchiol4 is a stable antioxidant and antibacterial with retinol-like properties; it inhibits the action of protein degrading enzymes while reducing inflammation. Tetra-hydrocurcuminoids, leuco-derivatives of curcuma longa root extract, can be used as powerful radical scavengers, while phytosterols from avocado and boswellia serrata extract are powerful anti-inflammatory and skin tonification ingredients. N-acyl ethanolamine is also a good anti-inflammatory agent.
Addition of pre- and pro-biotics sustain the resident microbial flora on the skin. Recently, a patent described the use of probiotic microorganisms, and/or fractions or metabolites of them, in conjunction with anti-dandruff actives, for preventing and treating dandruff. Unexpectedly, micro-organisms of the Lactobacillus sp. and/or Bifidobacterium sp. genus reduced dandruff conditions by acting on the hydration and barrier functions of the scalp.
These actions, according to the inventors, reinforce the barrier functions of the skin and reduce inflammatory conditions while preserving a balanced eco-flora. The scalp, in turn, is less irritated and fragile, and more hydrated. Furthermore, this treatment is reported to act more quickly and intensely than the isolated use of anti-dandruff agents.5
Pre-biotics like alfa glucan oligosaccharide are bio-selective ingredients, helping the development of protective microflora. Lactobacillus bulgaricus ferment filtrate is reported to increase cellular respiration and energy production, promoting collagen synthesis and fibroblast proliferation via β-defensin hBD2 gene expression. Lactococcus ferment lysate provides stimulation of skin renewal and recovery of the barrier function.
In the strategy of functional cleansing, ingredients promoting skin renewal and collagen synthesis are welcome: madecassicoside, asiaticoside and Hippophae rhamnoides extract have been recently used as skin revitalizers.
Each time we wash our hair and scalp, we challenge the osmotic equilibrium between our cells and their environment. Therefore, we should consider a way to compensate the induced osmotic stress.6 Osmolites are an underestimated category (in cosmetics) of small protecting molecules in skin and scalp treatment. Some of them have a zwitterionic nature, like betaines, ectoines and amino acids; others posess a polyols structure, like xylitol, threalose and myo-inositol. In human and plants physiology, osmolites can cross the cells membrane and buffer the difference of osmotic pressure between the inside and outside of living cells. Moreover, they protect proteins from hydrolytic denaturation and have moisturizing properties as they function as water movers.
New actives against scalp and hair disequilibrium
A supercritical CO2 extract from Apium graveolens—celery—containing the active molecule Senkyunolide, has been recently presented as a scalp-care ingredient. It reduced in a demonstrative study both dandruff and sebum production7. A new non-ionic conditioning agent, PPG-3 Caprylyl ether8 claims conditioning properties comparable to silicones by increasing strength and reducing hair damage. Moreover, as it improves silicone adsorption on hair cuticle, it can also be used in combination with silicones reducing the amount needed in the final formulation.
Allantoin Acetyl Methionine9 is a new compound with anti-seborrhoeic, anti-dandruff, anti-acne and healing properties. It represents an interesting combination of two well-known physiological ingredients like allantoin and methionine.
Back to the future
In the process of rediscovering traditional rituals, muds from the sea or lakes are finding growing interest in hair and scalp treatment. A carefully made massage with hydrated mud removes dirt, cleanses the skin and may infuse the hair and scalp with essential minerals. At the same time, mud treatments remove bacteria and keep the skin moisturized, purified and detoxified.
As pollution influences the scalp and hair biological and physical parameters—density, pH, bacteria, sweat and sebum, spots—mud treatment can reduce the impact of pollution on the scalp and hair. Moreover, its colloidal nature stimulates the skin’s natural defenses while reducing oxidative stress. As they leave a soft, hydrated colloidal layer, acting as a second-skin protective shield, the strengthening of the skin barrier is easily obtained.
- Zhang SG, Zhang JK, Zhu H, Ge SR Ageing effect on the diameter, nanomechanical properties and tactile perception of human hair. Int J Cosmet Sci (2016) 38, 155-163.
- Mucosave CG , Bionap Srl , technical brochure (2016)
- http://www.cosmeticsandtoiletries.com/research/patents/Patent-Pick-Anti-dandruff-ProbioticmdashNot-the-Contradiction-it-Seems-372995471.html (Accessed March 18, 2016)
- J Biol Chem (2004) Sep 24 279(39):40303-13.
- Technical data sheets Apiscalp (Croda) consulted April 2016
- Technical data sheets Softcare GP-1 (KAO) consulted April 2016
- www.in-cosmetics.com/en/exhibitors/392412/Akema-Srl/products/761786/ALMETH Consulted April 2016