Field of the invention The invention relates to an anti-perspirant composition that contains low or no aluminium salt.

Background of the invention Current anti-perspirant ingredients are based on aluminium, but inorganic salts have the effect of leaving white patches on clothes. Additionally there is a perceived health risk associated with aluminium. The current approach is to reduce the amount of aluminium in antiperspirants or to use additional metal salts such as those of zirconium. However, this approach tends to lower the efficacy of the formulation and hence prove more expensive. Zirconium-based antiperspirants tend to leave yellow patches on clothes.

US 2009/0016978 A1 (Courtois et al.) describes an antiperspirant composition comprising a carrier substance and a water-soluble or water-dispersible thiolated polymer. The prior art inventors believe that the thiol groups of the thiomer enable or enhance the polymer's ability to act as a mucoadhesive and that this ability enables or enhances the antiperspirant activity of the thiomer. "Mucoadhesives" are materials that can attach to mucin in a biological surface. The prior art inventors further believe that the antiperspirant activity results, at least in part, from the ability of the thiomers to act as pore blockers. The thiomers, when swollen by water, are thought to serve to as plugs that may, at least in part, block the exit of sweat from eccrine sweat glands. It is essential for the invention that the thiomer is water-soluble or water-dispersible in order for it to dissolve or disperse in eccrine sweat. WO 03/042251 (The Procter & Gamble Company) discloses compositions comprising chitosan in the form of a network of nano-sized fibres. Traditional chitosan is usually semi-crystalline and only soluble in acidic medium, typically in a pH range of from 1 to 5 limiting homogeneous formulation. A process for producing the network of nano- sized fibres is described involving the steps of forming an aqueous solution, neutralising the chitosan just to the point of precipitation, and homogenising the resulting suspension. It was observed that the minimum concentration of chitosan to inhibit Malassezia furfur (yeast implicated in dandruff) was lower than expected. This document also discloses an anti-dandruff composition comprising from about 0.01 % to about 5 %, preferably from about 0.5 % to about 2 % of chitosan by weight of the composition as the active anti-dandruff agent. The chitosan can be used in different applications, such as hair care, skin care, personal cleansing, odour control, wound care, blood management, oral care, film formation, controlled release of hydrophobic or hydrophilic materials, hard surface, fabric treatment, plant care, seed, grain, fruit and food protection, water purification and drug delivery. The chitosan compositions provide hair care benefits when formulated into products such as shampoos, conditioners, hairsprays, styling mousses and gels, hair tonics and hair colorants, especially anti-dandruff benefits and reduction of hair damage caused by the process of hair bleaching, permanent waving or coloration. Additionally, the compositions provide scalp benefits and conditioning properties such as softening, manageability and stylising of the hair. Specific examples are a shampoo, a conditioner, a dentifrice, a mouthwash, a non-abrasive gel, a chewing gum and a plant care composition.

WO 2006/040092 (Beiersdorf AG) discloses an aerosol formulation comprising one or more anti-perspirants and/or deodorising substances and chitosan having a degree of deacetylation of 75 to 98 %, a viscosity of 5 to 10 mPas, a weight average molecular weight distribution of less than 300 000 Da and a number average molecular weight distribution of less than 100 000 Da. It appears that the disclosed chitosan preserves the skin flora rather than acting purely as a bacteriocide. In particular, the chitosan appears to bind to the bacteria preventing microbial decomposition of sweat leading to odour. Anti-perspirants reduce sweat formation with the aid of astringent compounds in them, which are predominantly aluminium salts, such as aluminium hydrochloride, activated aluminium chlorohydrate or aluminium zirconium. It is customary to combine astringents with antimicrobials in the same composition. Aerosol products generally contain active anti-perspirant substances in the form of solids, which are suspended in an oil phase. Conventional active deodorant substances include ethyl hexyl glycerol, methyl phenyl butanol and polyglyceryl-2-caprate. One aim of the invention described in WO 2006/040092 is to reduce whiteness on skin or clothes. The formulation comprises 0.001-2, preferably 0.01 -1 , especially 0.015-0.3 % w/w chitosan. The formulation comprises 1 -35, preferably 1 -25, especially 1 -20 % w/w anti-perspirant component. The formulation comprises preferably 0.01-10, especially 0.05-5 % w/w deodorant component. Examples disclosed are anhydrous compositions. WO

2006/040092 further discloses that the pressure container used for the aerosol can be made of a metal, protected glass, non-shatter glass or some other glass, or else of a plastic. The propellant gas is preferably chosen from a long list of suitable gases.

US 2003/0133891 (Cognis Corporation) discloses a deodorising preparation containing nanoscale chitosans and/or chitosan derivatives with a particle diameter in the range from 10 to 300 nm. Chitosans have a bacteriostatic effect and a synergistic deodorising effect with esterase inhibitors and aluminium chlorohydrates. It is disclosed that absorption of nanoscale chitosans and/or chitosan derivatives by the Stratum Corneum is increased leading to long-lasting deodorising effect. The chitosan is normally used at levels of 0.01 -5, preferably 0.1 -1 , more particularly 0.2-0.6 % w/w. The document provides long lists of anti-perspirants based on salts of aluminium, zirconium or zinc, and deodorants. The preparations may contain 1 -50, preferably 5-30, particularly 10- 25 % w/w anti-perspirants. Specific examples of anhydrous anti-perspirant or deodorant suspension sticks and soft solids, deodorant cream emulsions, and oil-in- water roll-on and sprayable anti-perspirants / deodorants are provided. In particular a composition (composition 2 in table 2) is disclosed comprising the nanoscale chitosan, distearyl ether and dioctyl carbonate.

WO 03/072610 (Cognis Deutschland GmbH & Co. KG) discloses transparent cosmetic preparations containing chitosan and having a pH of below 6, comprising a) chitosan and/or chitosan derivatives, b) at least one anionic surfactant, c) at least one alkyl oligoglycoside, and d) water. Chitosans are valuable raw materials for use in cosmetics, because they have film-forming and moisturizing properties. They are also known to inhibit the activity of esterase-producing bacteria, so they are often incorporated into deodorants as well. Previously, it had been difficult to use them simultaneously with anionic surfactants, owing to the positive charge on them, leading to precipitation, which made the resulting preparation turbid. The document provides lists of anti-perspirants and esterase inhibitors. The preparations may contain 1 -50, preferably 5-30, particularly 10-25 % w/w anti-perspirants. Transparent anti- perspirants are claimed in claim 9. Examples of water-based clear cosmetic preparations containing chitosan and anionic surfactants are provided.

US 5 968 488 (Henkel KgA) discloses deodorizing preparations containing cationic biopolymers, aluminium chlorohydrate and esterase inhibitors. It has surprisingly been found that cationic biopolymers, preferably of the chitosan type, inhibit the activity of esterase-producing bacteria and that a synergistic deodorizing effect is obtained in conjunction with the two components mentioned above. The biopolymers have a bacteriostatic effect. At the same time, the use of the cationic biopolymers leads to an improvement in the dermatological compatibility of the products. Examples of water- based compositions are provided. US 5 968 488 further discloses use of propellant gases for spray applications. The formulations are preferably marketed as rollers (roll- on emulsion), sticks, deodorant sprays or pump sprays. WO 2015/058935 discloses the use of chitosan or a salt thereof as the sole anti- perspirant ingredient in an anti-perspirant composition.

A number of products comprising, amongst other things, chitosan have been launched. Thus Laverana has launched a deodorant spray and roll-on under their Lavera brand in Germany. The product was also claimed as an anti-perspirant.

Jukona has launched a deodorant gel comprising, amongst other things, chitosan, under their Jukona Rose brand in Germany. It was claimed as free from aluminium salts.

Scholl has launched in Belgium an anti-perspirant foot spray comprising chitosan and aluminium chlorohydrate menthyl lactate.

Natura Cosmeticos has launched a roll-on anti-perspirant deodorant under their Natura Kaiak brand in Argentina comprising chitosan and aluminium chlorohydrate.

Further improvements in this area would be desirable. Summary of the invention

The present inventors have found that high molecular weight chitosans or salts thereof provide a synergistic anti-perspirant combination with aluminium, zinc, magnesium and copper salts.

Thus in a first aspect, the present invention relates to an anti-perspirant composition comprising:

(a) chitosan or a salt thereof, with a weight average molecular weight of greater than 80 kDa; and

(b) an aluminium, zinc, magnesium or copper salt or mixtures thereof. wherein the composition comprises less than 3 wt% of aluminium salt. In a second aspect, the invention relates to a method of reducing perspiration from the surface of the human body comprising the topical application of a composition as described herein.

In a third aspect, the invention relates to the use of a composition described herein, in an anti-perspirant composition as an anti-perspirant ingredient.

Such compositions have been found to have a synergistically better performance than anti-perspirant formulations that comprise chitosan as sole anti-perspirant active or an aluminium, zinc, magnesium or copper salt as the sole anti-perspirant active.

Such combinations can therefore lead to more efficacious anti-perspirant formulations or to a reduction in the use of aluminium salts for a given anti-perspirant effectiveness or lead to formulations that use salts based on zinc, magnesium and/or copper. For the purposes of this invention the zinc and magnesium salts are preferred, with magnesium being the most preferred.

For the purposes of this specification, the term "anti-perspirant composition" means a composition which prevents or reduces the appearance of perspiration or sweat in humans. In a preferred embodiment, the composition will be packaged in a form which indicates to the consumer that the composition has an anti-perspirant effect, and in particular may contain the wording "antiperspirant" on the packaging. For the purposes of this specification, the term "anti-perspirant ingredient" means an ingredient which prevents or reduces the appearance of perspiration or sweat in humans.

For the purpose of this specification, the degree of acetylation is as measured using the dye-binding method (Gummow et al., Makromol. Chem., 186, 1239-1244 (1985)).

For the purposes of this specification the weight average molecular weight of chitosan may be determined by size exclusion chromatography. An example method involves dissolving 20 mg of chitosan in 1 % v/v aqueous formic acid. Polysaccharide reference standards are dissolved in the same diluent. Samples and standards are left to stand overnight to allow complete dissolution. Samples are prepared in duplicate. The analysis may be carried out on an Agilent 1200 series HPLC equipped with an ELSD detector. The chromatographic separation is achieved on an Agilent PL aquagel-OH MIXED H, 300 x 7.5 mm ID, 8 mm particle size GPC column, using a buffer of 0.01 M aqueous ammonium formate (0.1 % formic acid) at pH 3.1 as mobile phase, at a flow rate of 1 .0 ml.min-1.

Chitosan is a partially deacetylated form of the arthropod shell material chitin and is soluble in water at a pH of no more than 6.0. As well as from arthropods, chitosan and its precursor, chitin, are produced by fungi and bacteria, thus potentially providing a non-animal source for chitosan from a by-product of the fermentation industry.

Without being bound by theory, it is thought that when chitosan or a salt thereof is applied to the skin, it can diffuse into pores where it comes into contact with sweat, which has a pH of approximately 6.2 to 7.7, and precipitates forming a gel blocking the pores and reducing sweat flow. The gel formed is not permanent as it is hydrolysed over time. However the presence of the aluminium, zinc, magnesium or copper salt or mixture thereof is believed to greatly strengthen the formation of the gel in a synergistic manner or is involved in precipitation, or a chelation/bridging phenomenon owing to the metal ion.

Preferably the chitosan or salt thereof has a weight average molecular weight of greater than 100 kDa, preferably greater than 300 kDa, more preferably greater than 500 kDa, most preferably greater than 1000 kDa.

Preferably the chitosan or salt thereof has a degree of acetylation of 0-40 %. Preferred salts of chitosan are selected from the group consisting of acetate, chloride, citrate, formate, fumarate, gluconate, glycolate, lactate, maleate, malate, phosphate, propionate, succinate, sulphate, tartrate and mixtures thereof, preferably selected from the group consisting of formate, glycolate, lactate and mixtures thereof. Preferred salts are chlorides, sulphates and nitrates. Particular examples of suitable salts are aluminium chloride, aluminium chlorohydrate, zinc chloride, zinc sulphate, zinc nitrate, magnesium sulphate, magnesium chloride and copper chloride.

Preferably the anti-perspirant composition comprises 0.01 -5, preferably 0.01 -2, most preferably 0.01 -1 % w/w chitosan or chitosan salt.

Preferably the anti-perspirant composition comprises 0.01 -5, preferably 0.01 -2, most preferably 0.01 -1 % w/w aluminium, zinc, copper salt or mixture thereof. Preferably the anti-perspirant composition comprises less than 2 wt% aluminium salt, preferably less than 1 wt%, and most preferably is substantially or completely free of aluminium salt.

The chitosan or salt thereof is preferably either in an anhydrous form or dissolved in water at a pH of no more than 6.0, preferably no more than 5.5, most preferably no more than 5.0. The chitosan or salt thereof can be dissolved in water at a pH of at least 3.5, preferably at least 4.0, more preferably 4.5. Preferably a 0.5% wt/vol aqueous solution of the chitosan or salt thereof has an apparent viscosity of greater than 6.0, more preferably greater than 10.0 most preferably greater than 15.0 mPas at a shear rate of 100s ^"1 at room temperature. The composition may additionally comprise auxiliary ingredients selected from the group consisting of a fragrance, a bactericidal agent, a bacteriostatic agent, a perspiration absorber, an esterase inhibitor, a surfactant, a thickener, a chelator and a preservative. The composition preferably has a pH of from 3.0 to 6.0, preferably from 3.0 to 4.5, more preferably from 3.5 to 4.5.

Suitable bactericides include chlorinated aromatics such as biguanide derivatives of which triclosan (e.g. Irgasan DP300 or Triclorban), and chlorhexidine warrant specific mention. Another class of effective bactericide comprises polyaminopropyl biguanide salts such as are available under the trade mark Cosmosil.

Chelators that can sequester iron retard bacterial growth and thereby inhibit malodour formation. Examples include aminopolycarboxylates such as ethylenediamine tetraacetic acid (EDTA) or higher homologues such as diethylenetriamine pentaacetic acid (DTPA).

Bactericides and chelators are commonly employed at a concentration of from 0.1 to 5, and particularly 0.1 to 2 % w/w.

The composition can be in the form of a gel, or suitable for spray application, or suitable for application by aerosol, or suitable for application with a stick applicator. The method for their manufacture is well known to those skilled in the art. One preferred format is that the anti-perspirant composition is an aerosol composition comprising a volatile propellant.

As the composition is intended for use as an anti-perspirant composition, it is a leave- on composition, which means that the product is applied to the body without washing off with water at the time of application so that it is left on the body surface for a substantial period of time of e.g. a few or several hours at least.

The composition typically comprises less than 10 wt% surfactant and preferably less than 5 wt% surfactant. If any surfactant is present then it is preferably only of the non- ionic type and is substantially free of any other types of surfactants.

Preferably the composition comprises less than 10 wt% dipropyleneglycol, preferably less than 5 wt%. Preferably the composition comprises less than 10 wt% triglycerides, preferably less than 5 wt%. Such materials can provide the composition with an oily nature, which is undesirable in an anti-perspirant leave-on composition which is often in contact with clothing of a user.

Examples

Methods

This utilised 0.5 μΙ TLC dropper pipettes, manufactured by Camag and obtainable through VWR International, Lutterworth, UK. From the known volume (0.5 μΙ) and length of the capillary (3.2 cm) it was possible to calculate the internal diameter as 141 μηι.

Artificial sweat was drawn into a glass capillary (141 μηη aperture) under capillary action for one hour. The artificial sweat was of the following composition and adjusted to the appropriate pH with sodium hydroxide (default pH was 7.7 unless stated).

Artificial sweat of known pH (range 6.0-7.7) was drawn up the 141 μηι capillary by capillary action and the capillary was noted to be full within 5 seconds. The capillary was then suspended in a solution of the active to be tested at the concentration and pH desired for a period of 1 hour. The capillary was then removed from the active solution and allowed to dry for approximately 15 minutes before the break pressure

measurement was made. This permitted the observation of sweat breakthrough that would otherwise be masked by residual active solution on the outside of the capillary. The use of tissue to dry the capillary was avoided as this may have drawn out material from within the capillary.

The capillary to be measured for break pressure was inserted into the break pressure rig using the correct size adapter for the 141 μηη capillary. The hydrostatic pressure applied to the capillary was increased gradually at a rate of 0.05 ml/min until sweat was seen to emerge from the tip of the capillary. The pressure at which this occurred was noted and recorded.

After immersion in the active solution, the glass capillary was attached to the pressure sensor rig using the correct adapter for the 10 μηη capillaries. The hydrostatic pressure applied to the capillary was increased very gradually using a syringe pump set to dispense 0.2 ml/min of water. The pressure increase was monitored and recorded by a pressure sensor (OmegaDyne Inc., OH, USA, model PXM409, maximum of 1 Bar), with an instantaneous readout available on a computer screen using the software supplied by the sensor manufacturer (TRH Control, OmegaDyne Inc., OH, USA).

However in practice the maximum readable pressure is 800mBar due to the equipment attached to it. The pressure at which a visual breakthrough of water from the tip of the capillary is achieved is noted. Table 1 : Summary of Chitosan Sources

Error calculations

For all measurements of breakthrough pressures with 141 μηη capillaries, the error calculations have used the Standard Error of the Mean:

where

s is the sample standard deviation (i.e., the sample-based estimate of the standard deviation of the population), and

n is the size (number of observations) of the sample.

Example 1 : Effect of aluminium and chitosans as sole actives

Three commercially used antiperspirant actives based on aluminium have been tested with the capillary set up: aluminium chloride, aluminium chlorohydrate and AZAG (activated zirconium aluminium glycine). Aluminium chloride solutions were pH 4.6 (any higher causes precipitation), aluminium chlorohydrate and AZAG solutions were all pH 5.0. All were tested against pH 7.7 artificial sweat. The results are shown in Table 2. Table 2: Effect of Aluminium active (as sole active)

No real pore blocking effect was observed with these aluminium materials with the 141 μηη capillaries. Unbuffered higher concentrations up to 20% were evaluated, with no difference to the data but the pH of these solutions was as low as pH 1 and therefore unlikely to have been gelled by a weak buffer artificial sweat.

The three chitosans were tested for their pore-blocking capability. The results are shown in Table 3.

Table 3: Effect of Chitosans as sole active

Example 2: Effect of Combinations of Chitosans and Metal Salts to show a possible synergistic effect

The solutions of actives were made up by mixing chitosan and metal salt solutions so that the final concentrations of the individual components were 0, 0.01 , 0.5 or 0.1 % w/v and ph was 5.0 (in the case of Aluminium chloride combinations it was only possible to adjust to pH4.6 without precipitation).

Table 4: Various Chitosans or EDTA in combination with Aluminium Chloride

(AlC ₃ )

Table 5: Shrimp Chitosan + Aluminium Chlorohydrate (AICH)

Table 6: Various Chitosans or EDTA + AZAG (Activated Zirconium Aluminium Glycine complex)

Table 7: Various Chitosans + Zinc Chloride ZnCb

Table 8: Shrimp Chitosans + Zinc Sulphate ZnSQ ₄

Table 9: Shrimp Chitosan + Copper (II) Chloride CuCb Table 10: Shrimp Chitosan + Calcium Chloride (CaCI?)

Table 11: Shrimp Chitosan + Glycine

Table 12: 0.1 % Shrimp Chitosan with various metal salts

Table 13: 0.5% Aqua Chitosan with magnesium salts An effect has been observed with chitosans of high molecular weight (e.g. crab and shrimp chitosan) and aluminium, zinc, magnesium and copper salts whereby the pore blocking capability of the combination is greater than the sum of the pore blocking capability of the individual components at the same concentration.

The synergistic effect is not shown to be present between chitosan of high molecular weight (e.g. shrimp chitosan) and calcium chloride.

EDTA is a known chelating agent as it was considered that the chitosan may be chelating the divalent and trivalent salts to create the synergistic pore blocking effect. Glycine was also evaluated as a simple amino acid that was present as part of the AZAG complex.

The synergistic effect is also not shown to be present between chitosans of high molecular weight (e.g. shrimp chitosan) and glycine.

The synergistic effect is also not shown to be present between EDTA and aluminium salts.

Example 3: Speed of Gelation Assay

0.5 ml aliquots of the test chitosans in 100 mM acetic acid were carefully pipetted into a 2 ml Eppendorf. A weighed filter paper disc was pushed onto the surface with a plastic rod and 0.5 ml aliquots of 100 mM sodium hydroxide carefully pipetted on top. For the control tubes, the sodium hydroxide solution was removed and the filter paper taken out with forceps and dipped three times in distilled water. The washed paper was then left to dry at 50 °C in a forced-air oven for one hour on a weighing boat, then weighed. The same procedure was followed for the remaining tubes at known times. The initial rate of gelation was determined using the quadratic equation function in Microsoft™ Excel™.

The initial rates of gelation on the filter papers were:

0.50 % Shrimp Chitosan = 4 μg.min ^-1

At two concentration levels the speed of gelation is greater than the sum of the speeds of gelation of chitosan and zinc chloride separately.