Technically Speaking: UV Protection for Sensitive Skin

Feb 1, 2007 | Contact Author | By: Charles Fox, Independent Consultant
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Title: Technically Speaking: UV Protection for Sensitive Skin
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Skin and Skin Care

Peptides for collagen, hyaluronic acid production: Rohto Pharmaceutical Co. Ltd. describes peptides that increase collagen or hyaluronic acid production.1 The invention discloses a peptide having a specified amino acid sequence, or derivative or salt thereof, and relates to a composition containing the peptide or the like, a method of using the peptide or the like, use of peptide or the like, and a polynucleotide encoding the peptide or the like. The peptide of the invention can be used for enhancing production of at least one member selected from collagen and hyaluronic acid in a cell.

Surfactant stabilization of hydroquinone: N. Iimura et al. report on the development of new whitening agents using hydroquinone stabilized by the formation of complexes with surfactants. In addition, they report on their evaluation for melanogenesis inhibition and skin stimulus.2

Hydroquinone is well-known for skin depigmentation since it has been used clinically to inhibit melanogenesis. However, hydroquinone easily changes its structure when exposed to light, oxygen or heat. As a result, its color becomes brown or black. Iimura et al. have found that hydroquinone forms complexes with a variety of surfactant molecules. When a complex is formed, hydroquinone is stabilized without discoloration.

X-ray crystal structure analysis of the complexes revealed that the hydroquinone molecule becomes closely packed and covered with the surfactant molecules in the crystalline lattice. Among the complexes, a complex between hydroquinone and benzyl-hexadecyl-dimethylammonium chloride was examined in detail to establish its skin stimulus and safety. Moreover, the melanogenesis inhibitory effect was evaluated clinically. In every examination, the complex showed a good indication for the whitening agent. 

 Sunscreen antioxidant: Damiani et al. describe the synthesis and application of a novel sunscreen antioxidant.3 Background information on the insufficient free radical protection of the skin by sunscreens, despite their usefulness in preventing sunburn and erythema, prompted the investigators to synthesize a compound that would display both UV-absorbing and antioxidant capacities in the same molecule. 

For this purpose, the UVB absorber 2-ethylhexyl-4-methoxycinnamate (OMC) was combined with the piperidine nitroxide Tempol, which has antioxidant properties. Researchers studied the spectral properties of the new nitroxide-based sunscreen (MC-NO) and its efficacy to prevent photooxidative damage to lipids induced by UVA, natural sunlight and 4-tert-butyl-4-methoxydibenzoylmethane (BMDBM)—a photo-unstable sunscreen that generates free radicals upon UV radiation. 

The results obtained demonstrate that MC-NO absorbs in the UVB region even after UVA irradiation; acts as a free radical scavenger as demonstrated by EPR experiments; strongly reduces both UVA-, sunlight- and BMDBM-induced lipid peroxidation in liposomes, measured as reduced TBARS levels; and has comparable antioxidant activity to that of commonly used vitamin E and BHT in skin care formulations. These results suggest that the use of the novel sunscreen antioxidant or of other nitroxide-based sunscreens in formulations aimed at reducing photoinduced skin damage may be envisaged.


Galactose derivatives for antiseptic enhancement: Kao Corp. of Japan discloses antiseptic activity enhancers containing galactose derivatives.4 Agents that enhance the antiseptic activity of preservatives, even at low preservative concentrations, contain amphiphilic galactose derivatives as the active component. Antiseptic power-enhancing compositions containing 0.01–30% amphiphilic galactose derivatives and 0.01–1.0% preservatives, have applications in makeup, drugs, detergents and food. Thus, a composition at pH 6.5 containing 0.10% α, β-n-dodecyl galactoside and 0.075% methylparaben and the balance water showed satisfactory antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa after nine days at 30°C, whereas the same amount of methylparaben without the galactose derivative had low activity. 


HHM-HEC/lipophilic surfactant emulsification system: E. Akiyama et al. examined the mechanism of o/w emulsification using a water-soluble amphiphilic polymer and lipophilic surfactant.5 A new o/w emulsification system was developed using the amphiphilic polymer hydrophobically-hydrophilically modified hydroxyethylcellulose (HHM-HEC) and a lipophilic surfactant. HHM-HEC was used as a thickener and polymeric surfactant and the addition of small quantities of various types of nonionic lipophilic surfactant—hydrophilic-lipophilic balance <5—decreased the droplet size of several types of oil due to a lowering of the tension at the water/oil interface. The oil droplets were held by the strong network structure of the aqueous HHM-HEC solution, preserving the o/w phase without inversion. These stable o/w emulsions were prepared without the addition of hydrophilic surfactants and thus show improved water repellency. 

The TTS principle and emulsions: Muehlbach et al. reported on a study of the transferability of the time temperature superposition (TTS) principle to emulsions.6 The instability of emulsions basically is clarified by a phase separation. The separated phase can either cream or sediment. Destabilization mostly is compounded by coalescence and gives a first indication through extension of droplets. 

In the cosmetics industry as well as others, product stability is one of the most important quality criteria. Many stability tests already have been performed with the widest variety of methods from different fields of technology. In R&D it is especially important to obtain quick results on the stability of a formulation. Such results represent a tool that can help developers to find an optimal formulation in a short time. In addition, they can shorten development times, leading to quicker introduction of a product in the market. Moreover, they can help to reduce storage stability tests to a minimum, making less climatized rooms, space and work required to predict shelf lives. 

The cycle test is an example of such a method developed in the field of rheology. In this test, the sample is subjected to continuously changing temperatures and its behavior observed. However, other methods also can conceivably be used to predict stabilities. The aim of this current work is to find a new model to predict long-term stability. Such a model should be based on empirical data and it should determine the applicability of the time temperature superposition (TTS) principle to emulsions. 

PEG-free emulsifier: J. Meyer et al. have published on a novel PEG-free emulsifier designed for formulating w/o lotions with a light skin feel.7 The newly developed w/o emulsifier polyglyceryl-4 diisostearate/polyhydroxystearate/sebacate enables the formulation of PEG-free w/o emulsions with a light skin feel because it enables the formation of stable w/o lotions with oil phase contents as low as 18–20%wt. In particular, when polyglyceryl-4 diisostearate/polyhydroxystearate/sebacate is used in combination with light emollients such as diethylhexyl carbonate or cyclopentasiloxane, w/o lotions with a very light skin feel can be obtained. Moreover, the stabilizing potential of the new emulsifier proved to be outstanding even under critical processing conditions, providing formulators a tool to develop formulations combining attractive sensory profiles with specific advantages of w/o emulsions. 


UV protection for sensitive skin: Hewitt has published an article discussing formulating approaches to incorporating UV protection in daily use skin care products, in particular those targeted at sensitive skins.8 The ideal product: should have an SPF of 8–15, be easy to apply and transparent on skin, incorporate mild ingredients, and confer other benefits such as good moisturization. Inorganic sunscreens have an advantage in formulations for sensitive skin because of their mildness; however, they are not often used because of whitening on skin and poor skin feel. 

New developments in titanium dioxide technology provide good transparency and sensory properties. The choice of emollients can be aided by considering the inherent sensory and clinical properties of emollients. A number of suitable emollients are available that offer benefits such as moisturization and are good solvents for UV filters. Emulsifiers can also influence skin feel and efficacy. Systems based on lamellar gel networks are advantageous because of the moisturizing effects they offer. Some novel w/o emulsions also can deliver a high degree of cosmetic elegance. 

Makeup/Makeup Removers

Mild makeup remover: Unilever N.V., the Netherlands, discloses cosmetic makeup remover compositions containing polyols and glycerol triisostearate esters.9 The invention relates to a cosmetic makeup remover composition having excellent makeup-removing effects that is mild to skin. The composition is characterized by containing 0.50–40 parts total polyol, a glycerol triisostearate ester—especially alkoxylated glyceryl triisostearate, e.g. 0.50–20% polyethylene glycol (20) glyceryl triisostearate—and water. An example is shown in Formula 1.

Interesting Vehicles

Ubiquinones in stable aqueous formulas: Kosei Co. Ltd. describes transparent aqueous compositions containing ubiquinones.10 This invention relates to stable transparent aqueous preparations containing 0.0001–0.05% ubiquinones and 0.0005–0.12% oils. The composition may further comprise solubilizing agents and lower alcohols. An example of such a lotion is shown in Formula 2.

A nonwater gel comprising PEG: Nihei et al. have studied the gelation mechanism of a nonwater gel comprising PEG.11 The researchers developed a nonwater gel comprised of PEG and hydroxypropyl cellulose (HPC) as a gelling agent. They investigated the gelation mechanism of the HPC/PEG system on the basis of a stress-controlled rheometer and an x-ray diffractometer. From these results, they found that two gelation mechanisms coexisted in the HPC/PEG system: the entanglement of interacting HPC polymer chains, that behave like a flexible polymer, and the cross-linking of the microcrystalline domains of the HPC main chains. In the lower HPC concentration range, the gelation is dominated by the cross-linking of the microcrystalline domains of the HPC main chains. On the other hand, in the higher HPC concentration range, the gelation is dominated by the entanglement of interacting HPC polymer chains. 

Interesting Raw Materials

Biomimetic phospholipids: Uniqema describes further applications of biomimetic phospholipids.12 A previous research disclosure described the use of compounds in wipes and antiperspirant/deodorant applications and stated that the use of these products can allow the level of an antimicrobial agent (for example, triclosan) to be reduced without decreasing the functional effect. 

This reduction in concentration, and in some cases even elimination, of an antimicrobial agent also can be achieved in other applications. These include: anti-acne products such as cleansers, mousses, creams, lotions, sticks and wipes; oral care products such as toothpastes and mouthwashes; shaving and aftershave preparations such as shaving creams, gels, foams and balms; rinse-off antimicrobial cleansing formulations for body, face, and hands—containing no antimicrobial agent such as triclosan, an acid and/or acid anhydride buffer; and antidandruff and antibacterial hair shampoo such as rinse-off and leave-on formulations.13 

Rheology modifier: Kwek et al. report on a rheology modifier mixture of acrylates/steareth-20 methacrylate crosspolymera and laponite clay.14 The acrylates/steareth-20 methacrylate crosspolymer displays synergy with laponite clay, reportedly enabling viscosity building and suspension in a wide range of surfactant, soap-based, and nonsurfactant-containing formulations. 

Various neutralizing agents can be used with the crosspolymer, including potassium hydroxide, sodium hydroxide and aminomethylpropanol; it also can be combined with laponite clay or a variety of other rheology modifiers. Representative shower gel formulations containing the crosspolymer in combination with laponite clay are described.

Cationic emulsifier systems for sunscreens: Jenni et al. describe cationic emulsifier systems for sunscreens that combine efficacy with a cost advantage.15 Cationic emulsions have attracted increased interest recently because of their unique skin feel that is more dry and powdery than that of anionic or nonionic emulsions. Cationic emulsions also can help to improve the moisturization level of aged skin. 

Because of their unique film-forming efficacy, cationic emulsifiers allow formulators to prepare 100% water-resistant emulsions without the addition of a film former. They are compatible with many types of sunscreens filter systems, except for benzimidazole sulfonic acid derivatives. These properties make them a versatile and cost-efficient alternative to conventional emulsifiers in sunscreens. 

HMI for stabilization of formulas: Tharwat et al. discuss the application of polymeric surfactants in cosmetics and personal care products, dealing specifically with a novel polymeric surfactant of hydrophobically modified inulin (polyfructose).16 The use of polymeric surfactants for stabilization of cosmetic and personal care formulations is described in terms of their adsorption and conformation at the solid/liquid and liquid/liquid interface. The most effective polymeric surfactants are the A-B, A-B-A block and BAn or ABn graft types, where B is the anchor chain and A is the stabilizing chain. 

The mechanism by which these polymeric surfactants stabilize suspensions and emulsions is briefly discussed. In terms of their interaction on approach of particles or droplets, a very strong repulsion is created, referred to as steric stabilization. Particular attention was given to a recently developed graft copolymer ABn based on inulin extracted from chicory roots that is hydrophobized by grafting several alkyl groups (B) on the linear polyfructose chain (A). This polymeric surfactant is referred to as hydrophobically modified inulin (HMI) and is commercially availableb

This polymeric surfactant was used for stabilization of o/w emulsions both in aqueous media and in the presence of high electrolyte concentrations. The emulsions remained stable for more than one year at room temperature and at 50°C. The material is effective in reducing Ostwald ripening in nanoemulsions and could be applied for the preparation of w/o/w and o/w/o multiple emulsions as well as used for stabilization of liposomes and vesicles. 

Based on these fundamental studies, the materials could be applied for the preparation of stable personal care formulations. The amount of polymeric surfactant required for maintenance of stability (for more than one year at ambient temp.) was relatively low—on the order of 1% wt/wt based on the oil phase. In addition, the polymeric surfactant showed no skin irritation, stickiness or greasiness and gave an excellent skin feel. 

Anthranilic acid amides as antioxidants: Schmaus et al. described the use of anthranilic acid amides as antioxidants in food, functional food, cosmetic and pharmaceutical compositions.17 Compositions comprising at least one synthetic anthranilic acid amide or an extract of biological origin such as Avena sativa (oat) or Dianthus sp. (carnation) containing anthranilic acid amides with potent antioxidant activity are disclosed. In particular, the use of preferentially anthranilic acid amides named avenanthramide D, dihydroavenanthramide D, avenanthramide E, and dihydroavenanthramide E as antioxidants are considered. 

Sodium metabisulfite/glutathione on the stability of vitamin C: A.M. Maia et al. published on the influence of sodium metabisulfite and glutathione on the stability of vitamin C in o/w emulsion and aqueous gels.18 Vitamin C exerts several functions on skin such as collagen synthesis and depigmenting and antioxidant activities. Vitamin C is unstable in the presence of oxygen, luminosity, humidity, high temperatures and heavy metals, which presents a significant challenge to the development of cosmetic formulations. Therefore, the utilization of an effective antioxidant system is required to maintain the vitamin C stability. 

The purpose of this work was to develop prototypes of cosmetic formulations in the forms of o/w emulsions and aqueous gels containing vitamin C and to evaluate the influence of sodium metabisulfite (SMB) and glutathione (GLT) as antioxidants on the stability of the active substance. An HPLC stability-indicating method was developed and validated for this study and stability assays were performed in 90 and 26 days; storage conditions were 5.0±0.5, 24±2 and 40.0±0.5°C. Preparations with SMB or GLT and the antioxidant-free preparation presented results statistically distinct, demonstrating the necessity of the antioxidant system. O/W emulsions with SMB or GLT retained the vitamin C 

content >90.38% stored at 5.0±0.5 and 24±2°C. For the aqueous gels with SMB or GLT, the active substance concentration was maintained >94.03%. Considering the vitamin C stability, the SMB and the GLT were shown to be statistically adequate as antioxidants for the cosmetic formulations. 


1. WO 2006 101,187, Peptides that increase collagen or hyaluronic acid production, Rohto Pharmaceutical Co Ltd, Japan (Sep 28, 2006)

2. N Iimura et al, Development of new whitening agents with hydroquinone stabilized by the complex formation with surfactants and the evaluation for melanogenesis inhibitory effect and skin stimulus, Nippon Koshohin Gakkaishi 29 4 301–313 (2005) (in Japanese)

3. E Damiani et al, Synthesis and application of a novel sunscreen-antioxidant, Free Radical Research 40 5 485–494 (2006) (in English)

4. JP 2006 241,064, Antiseptic activity enhancers containing galactose derivatives, Kao Corp, Japan (Sep 14, 2006)

5. E Akiyama et al, Mechanism of oil-in-water\ emulsification using a water-soluble amphiphilic polymer and lipophilic surfactant, J of Colloid and Interface Sci 300 1 141-148 (2006) 

6. M Muehlbach et al, Study on the transferability of the time temperature superposition principle to emulsions, Intl J of Cosm Sci 28 2 109–116 (2006) (in English)

7. J Meyer et al, A novel PEG-free emulsifier designed for formulating w/o lotions with a light skin feel , SOFW 131 11 20–22, 24–26, 28 (2005) (in English)

8. JP Hewitt, Formulating for tomorrow: UV protection in daily use skin care, Chimica Oggi 34–35, 38-40 suppl (2006) (in English)

9. JP 2006 241,151, Cosmetic makeup remover compositions containing polyols and glycerol triisostearate esters, Unilever N.V., Netherlands (Sep 14, 2006)

10. JP 2006 241,075, Transparent aqueous compositions containing ubiquinones, Kosei Co Ltd, Japan (Sep 14, 2006)

11. T Nihei et al, The gelation mechanism of non-water gel comprising PEG, Nihon Reoroji Gakkaishi 34 2 83–89 (2006) (in Japanese)

12. Uniqema (UK), Further applications of biomimetic phospholipids, Research Disclosure 497 No. 497009 962–963 (Sep 2005) (in English)

13. Harry’s Cosmeticology, 8th edition, M.M. Rieger, ed., Chemical Pub. Co., New York: 408–411 (2000) 

14. Kwek Wee Tin et al , AculynT 88 rheology modifier and laponite clay, Research Disclosure  500 No. 500002 1375–1376 (Dec 2005) (in English)

15. K Jenni et al, Cationic emulsifier systems for sunscreens. Combining efficacy with cost advantage, Chimica Oggi 27–30 suppl (2006) (in English)

16. T Tharwat et al, Application of polymeric surfactants in cosmetics and personal care. A novel polymeric surfactant of hydrophobically modified inulin (polyfructose), Chimica Oggi 55–58 suppl (2006) (in English)

17. G Schmaus et al, Use of anthranilic acid amides as antioxidants in food, functional food, cosmetic and pharmaceutical compositions, Research Disclosure 506 No. 506003 669–672 (Jun 2006) (in English)

18. AM Maia et al, Influence of sodium metabisulfite and glutathione on the stability of vitamin C in o/w emulsion and extemporaneous aqueous gel, Intl J of Pharmaceutics 322 1-2 130–135 (2006) (in English)                  



Fox: UV Proection Footnotes

aAculyn 88 Rheology modifier (INCI: Acrylates/steareth-20 methacrylate crosspolymer) is a product of Rohm and Haas. 

bInutec SP1 (INCI: Inulin lauryl carbamate) is a product of Orafti.

Formula 1. Cosmetic makeup remover

Formula 1. Cosmetic makeup remover9 

Formula 2. Transparent aqueous lotion with ubiquinone

 Formula 2. Transparent aqueous lotion with ubiquinone10

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