Strategies for Hair Repair, Strengthening and Growth


Consumers dedicate an impressive amount of time over the course of a lifetime to cleaning and styling hair, and managing its luster and sensorial appeal, but many daily treatments can damage the hair—notably harsh shampoos, heavy brushing and combing, as well as frequent exposure to chemicals, e.g., from perms, bleaching and dyes.

Moreover, environmental stressors including excessive exposure to sun and salt water, very dry or humid atmospheres, and absorption of city pollutants pose risks to the integrity of hair structure. Finally, aging phenomena contribute to decreases in the speed of hair renewal, weakening the keratin structures and producing thinner and less structured hair shafts.

Many approaches can be used to fight these phenomena. These include: repairing hair structure to recover as much of its integrity as possible; treating hair with specified ingredients to increase its strength and resilience; and directly acting on the scalp to promote hair growth. The practical application of these strategies is described here.

The Right Vehicles

Before delving into active solutions, it is important to consider that any hair care treatment must take into account a few major factors. The appearance of the treated hair must be pleasant and shiny, and its feel soft and manageable. The amount of residue left on the scalp and the hair should be negligible and non-noticeable. Also, for leave-on products, the drying time should be fairly fast. In other words, any vehicle for hair treatments should provide a perceivable hair conditioning effect without any stickiness or excessive build-up.

Generally, hydro-alcoholic vehicles are preferred. By careful management of the alcohol content and hydrotropes, i.e. humectants, one can create a fairly quick-drying system with adequate solvent power for all lipophilic active principles, refreshing effects through alcohol evaporation and satisfactory hair manageability. Moreover, hydro-alcoholic systems homogenously redistribute sebum from the roots and scalp, giving hair good manageability and a soft feel.

In some cases, oil vehicles also are used. When diluted with volatile silicone, these can provide a light application feel. Oils supply the hair with gloss and shine, especially in the case of damaged hair, as they modify the interference of incident light with the hair shaft. So-called dry oils such as isopropyl myristate and di-isopropyl adipate are typically preferred because their residual feel on hair is non-greasy.

Another way to distribute ingredients in hair without excessive build-up is via a quick-breaking foam. Its initial voluminous application thoroughly wets hair, and after the solvent evaporates and the propellant disappears, the formula evolves to leave a soft-touch coating on hair. Of course, rinse-off products like conditioners and hair masks might also be employed. In such cases, the conditioning effect is provided by monomeric or polymeric cationics and substantive active principles. These latter compositions include a broader selection of active molecules, as such formulae may associate in the form of an emulsion, being hydrosoluble with lipophilic ingredients. Both leave-on and rinse-off conditioners employ a variety of ingredients, including cationic surfactants, polymers, emollients and humectants. An example is shown in Formula 1.1

Here, tamanu oil is said to recondition the hair structure and help prevent split ends. The conditioning effect is provided by the combination of an added, pre-formed cationic and amido-amine, which is cationized by the citric acid. The cationics also emulsify the oils. The resulting emulsion is stabilized by cetearyl alcohol, while the other hydrosoluble actives protect the hair surface. In a variation2 of this formula, Ceramide III in phase B and creatine in the water phase are used as alternative actives. The preparation procedure is simple: mix A and heat to 80°C; add B and homogenize; begin cooling at 50°C, then add C and mix until uniform; add D, mix and cool to room temperature.

Protection and Repair

Cationic polymers: Cationic polymers provide hair with slip, manageability and combability. They increase body in damaged hair and can improve split ends. Their use must be carefully controlled since excessive amounts can lead to progressive build-up in the hair, making it feel heavy and greasy. Percentages between 0.5% and 2% are recommended. Frequently, blends of two different cationics are used to optimize feel and protection performance.

Emollients: Emollients provide a uniform film on the surface of hair. Long, branched-chain saturated hydrocarbons are most often used. For example, low molecular weight hydrogenated polydecenes and poly-isobutenes; esters with a high refractive index (i.e., the whole family of isostearyl esters); and silicones with phenyl chains. These latter ingredients are very hydrophobic, and capable of waterproofing hair, in order to protect it from environmental damage.3

Humectants: Humectants promote water retention, a mechanism that is helpful to controlling the brittleness of hair. Traditional polyols such as glycerin and di-glycerin are most commonly used, although the osmotic protectants betaine and trehalose have recently been introduced. Isopentyldiol also is increasingly being used at 1-5% for its lightness and silky final touch.4

Sunscreens: Another way to protect hair from UV rays is to treat it with quaternized UV filters, which are compatible with anionic surfactants.5

Considering all these mechanisms of protection and repair, an example of a moisturizing, deeply penetrating conditioner is shown in Formula 2.6 This formula is said to provide easy wet-combing (reducing hair breakage), impart a smooth seal and realign damaged areas of the hair shaft. Further, it minimizes porosity and provides some protection against thermal and mechanical damage. To increase its adsorption, the formula can be applied to hair and worn under a plastic cap for 20 to 30 min under a warm dryer.

This formula also emphasizes the more recent use of D-panthenol in hair care. While both D,L-panthenol and D-panthenol have been utilized, some believe the “real” active in the DL racemic blend is only the “D” molecule, and it must be kept at a fairly low temperature to avoid its racemization. Sodium PCA also is included in this formula. A known water coordinator, the ingredient’s two quaternaries associate to provide optimum cuticle conditioning without excessive build-up. The emollient after-feel of this conditioner is provided by cetyl alcohol, which also stabilizes the emulsion, while the spherical-shaped molecules of hydrogenated polydecene act as a lubricant, deeply penetrating into the hair fibers by diffusion.

The preparation of this formula is as follows: mix A and heat to 80°C; add B to A at 80°C; mix for 30 min, then cool to 40°C; add C while mixing, then cool to room temperature. As an energy efficient alternative, one could consider adopting Lin’s method of low energy emulsification.7 Using this technique, only 20% of the total water requires heating to 80°C. The hot, aqueous A must then be added very slowly at first, then progressively faster, to the molten B under good homogenization for 10 min. After complete emulsification, the remaining cool water is added slowly while mixing. Cooling the batch to room temperature and adding perfume will complete the process.


An intact cuticle is responsible for the strength, shine, smoothness, softness and manageability of hair. Once hair is damaged it cannot be repaired, even by conditioning agents. Such ingredients affect the hair cuticle by sealing it, temporarily improving the cosmetic value and appearance of hair. They also improve sheen and decrease brittleness and porosity. In this way, they provide strength—in the sense that they increase hair’s resistance to breakage during combing.8

It is important to note that hair strength, according to consumer language, can mean something different than the technical measure of hair’s resistance to a force. Therefore, strength can be measured in different ways and, consequently, many good conditioners satisfy the consumer requirement for strength and quantified by the work necessary to comb hair. Another interesting measure is the so-called flexabrasion test (for more on this, see Page 38),9 which takes into account several physical processes involved in hair fracturing, including fiber bending, abrasion and extension.

Hair Growth

Hair reinforcement also means increasing the number of telogen hairs. The activation of certain parts of the hair follicles (i.e., the outer root sheath, hair matrix and papilla) is necessary for the hair growth cycle.10 In relation, the well-known minoxidil hair growth ingredient has paved the way for many other effective molecules. For instance, a mixture of vegetal proanthocyanidins with anti-inflammatory activities and strong antioxidant effects has been demonstrated to activate the proliferation of murine hair epithelial cells. With this treatment, a six-month human clinical trial demonstrated improvements in hair density and diameter. Here, it has been surmised that the suppression of inflammation helps to return the scalp to a healthy condition.

Formula 3 shows an example lotion to treat hair loss. To prepare it: mix A in order at room temperature; prepare B and add with stirring to A; and filter the batch 24 hr later. In this formula, the trans-epidermal delivery of the actives panthenol and biotin to the scalp is ensured by the ethoxydiglycol, and hydrolyzed proteins form a protective coating on the hair. Some additional alcohol, ~20%, would have avoided the use of preservatives and solubilizers while accelerating the product’s evaporation.

Formula 4 is an example hair tonic in which alcohol helps to dissolve the lipophilic vitamins and actives. Butylene glycol adjusts the evaporation of the formula and assists the transdermal delivery of the actives. The emulsifier supports the lotion in wetting the scalp, and a small amount of a specialized n-acetylated ester provides luster to the treated hair.

Advances in Anti-hair Loss Actives

Among the recently commercialized actives to fight hair loss, a blend of skin-identical sphingolipids from Evonika prevents hair loss by addressing scalp health and rebalancing the hair lifecycle. This active inhibits 5-α-reductase, a well-known antagonist of the hair cycle, and thus improves the scalp’s renewal capacity. Another combinationb of three plant extracts—Scutellaria baicalensis, Triticum vulgare and Glycine max—from Provital Group is said to activate follicle stem cells. Also, synthetic versions of thymus peptides have been found to treat telogen effluvium and androgenetic alopecia.11

Henkel12 has demonstrated that a combination of caffeine and taurine, when applied topically to the scalp, reduces premature hair loss and positively influences hair growth. And another combinationc of Trifolium pretense (red clover) extract with a biomimetic peptide (discovered and developed by Lucas Meyer Cosmetics) works by inhibiting 5-α-reductase activity, reducing inflammatory reactions and stimulating extracellular matrix protein synthesis near the hair follicle.13 Finally, Neocell’s Keratin Hair Volumizer product contains ingredients that enhance hair strength and reduce hair loss, notably: solubilized keratin, hydrolyzed collagen, Indian Gooseberry extract (amla) and vitamin C.14

When All Else Fails

As an alternative to improving the strength of hair, one can now micro-pigment the scalp to give the realistic illusion of shaven hair.15 There is also an option to sprinkle tiny filaments onto thinning hair to make it appear more voluminous;16 the same can be accomplished using microscopic hair fibers.17


  1. M Westman, New shampoo technologies: Between the shock waves, Cosm & Toil 118 (5) 57-64 (2003)
  2. Centerchem formula, in Hair Care Formulation for All Hair Types, P Romanowski, ed, Allured Business Media, Carol Stream, IL USA, 27 (2011)
  3. R Schueller and P Romanowsaki, Fundamentals of formulating hair care products, Cosm & Toil 115(10) 67-73 (2000)
  4. L Rigano and N Lionetti, Isopentyldiol for improved sensory, formulation and manufacturing benefits Cosm & Toil 128(6) 12 (2013)
  5. P Vanemon, Photoprotection of human hair, Cosm & Toil 113(6) 77-9 (1998)
  6. AN Sayed, in Hair and Hair Care, DH Johnson, ed, Marcel Dekker Inc., New York City (1997) p 253, modified
  7. TJ Lin, Manufacturing Cosmetic Emulsions, Allured Business Media, Carol Stream, IL USA (2010)
  8. C Rocafort, E Bazemore and E Werner, Asian hair: Its properties, physiology protection and the market for Asian hair care, Cosm & Toil 119(2) 53-8 (2004)
  9. JA Swift, SP Chahal, DL Coulson and NI Challoner, Flexabrasion: A method for evaluating hair strength, Cosm & Toil 116(12) 53-9 (2001) [see Page 38 of this issue]
  10. T Takahashi, A Kamimura, Y Yokoo and Y Watanabe, Procyanidin B-2 and the hair-growing activity of proanthocyanidins, Cosm & Toil 116(12) 61-72 (2001)
  11. (Accessed Apr 23, 2014)
  12. T Welss et al, Synergistic effects of taurine and caffeine on the regulation of the hair cycle: Composition of bioactives against premature hair loss, IFSCC Magazine (2)81 (2012)
  13. E Loing, R Lachance, V Ollier and M Hocquaux, A new strategy to modulate alopecia using a combination of two specific and unique ingredients, IFSCC Magazine (2)45-58 (2013)
  14. (Accessed Apr 23, 2014)
  15. (Accessed Apr 15, 2014)
  16. (Accessed Apr 23, 2014)
  17. (Accessed Apr 23, 2014)


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