Creative Developments
(Cosmetics) Limited
Antiperspirants
& Deodorants 1999
The
causes of body malodour and the theory behind antiperspirant activity have been
covered in previous articles appearing in Manufacturing Chemist (August ‘95,
August ‘96) and a complete list of permitted actives was published in the 1994
issue and the focus in ‘97 was on methods of improving the delivery of the
active. This feature will look at further developments in improving the
efficacy of the active and the quality of the product, at recent patent
activity and at various proposals for reducing perspiration and body odour
without the use of aluminium salts or antimicrobial materials.
The
first deodorants relied on strong perfumes to mask body odour. When it was
realised that the source of the odour was microbial breakdown of triglycerides
of fatty acids such as propionic, butyric and hexanoic acid antimicrobial
products were introduced. One early formula contained 1% formaldehyde! The use
of aluminium salts to reduce perspiration appears to predate the use of antimicrobials;
although used primarily to reduce wetness they also reduce the feed stock for
bacterial breakdown and they are now known to have recognisable antimicrobial
properties. With development of antiperspirant materials restricted by
legislation in Europe and the USA formulation improvements have been aimed at
enhancing the activity of permitted aluminium salts and aluminium-zirconium
complexes, with improving product texture and aesthetic appeal and particularly
with reducing residual whiteness.
The
major manufacturers of antiperspirant actives are constantly striving to
improve the activity of the material within the parameters defined by current
legislation. Dr. Allan Rosenberg of Summit
Research reports [Ref. 1] that further studies concerning the polymer
distribution and molecular size of aluminium and aluminium-zirconium systems
have been correlated to clinical efficacy studies to determine optimum
distribution for enhanced efficacy. By using propriety manufacturing techniques
Rosenberg reports that new powders having optimum performance are being
produced such as the aluminum zirconium trichlorohydrex gly, AAZG-7160 and the
aluminum zirconium tetrachlorohydrex gly, AAZG-7167. Formula I illustrates the
use of an enhanced efficacy active in a soft-solid antiperspirant.
Formula I: Soft-Solid Antiperspirant
|
Ingredient |
% w/w |
Source |
|
Cyclopentasiloxane |
50.00 |
Generic |
|
Phenyl trimethicone |
6.00 |
Generic |
|
Stearyl alcohol |
2.00 |
Generic |
|
PPG-14 butyl ether |
5.00 |
Ucon Fluid AP; Amerchol Corp. |
|
Hydrogenated castor oil |
3.00 |
Castorwax MP-80; Caschem |
|
Fumed silica |
3.00 |
Cab-o-sil M5; Cabot Corp. |
|
Starch |
7.00 |
Dry-Flo PC; National Starch |
|
Aluminum zirconium tetrachlorhydrex Gly |
24.00 |
Enhanced Efficacy AAZG-7167; Summit Research . |
Enhanced
efficacy actives are also available from Summit as spherical beads in particle
sizes of 15, 25 or 35 microns. When incorporated in stick products they are said
to show less white residue than from clear sticks; formula II is an example
formulation of a low residue anhydrous antiperspirant stick.
Formula II: Low residue antiperspirant stick
|
Ingredient |
% w/w |
Source |
|
Cyclopentasiloxane |
32.50 |
Generic |
|
Polyoxypropylene (15) stearyl ether |
14.00 |
Arlamol E; ICI Surfactants |
|
Stearyl alcohol |
20.00 |
Generic |
|
Isopropyl myristate |
2.00 |
Generic |
|
Hydrogenated castor oil |
3.00 |
Castorwax MP-80; Caschem |
|
PEG-8 distearate |
1.00 |
Generic |
|
Enhanced Efficacy AAZG-6313-15 Spherical Beads |
24.00 |
Summit Research . |
All
ingredients except the AAZG-6313 are heated to 82oC until melted and
clear, the AAZG-6313 beads are slowly stirred while maintaining the temperature
at 82oC. The mix is cooled with continuous stirring and poured at 49oC.
According
to David Fondots of Reheis a
major disadvantage consumers associate with many solid form antiperspirants is
that they often leave a noticeable white residue on skin and clothing after
application. A recommended optimum approach to formulating antiperspirant
sticks with less visible product residue is to partially substitute
non-volatile silicone, and, more importantly, to incorporate antiperspirant
actives with special physical properties. Reheis has developed a process for
the production of polyol-antiperspirant salts as relatively large spherical
shaped particles of high density and low surface area/mass ratios. Four new
actives were introduced at the IFSCC Congress and Exhibition in Cannes, 1998
and according to Fondots they are particularly well suited to provide low
residue properties in conventional opaque stick and roll-on compositions and
are preferred in formulas where a lower glycol content is desired. The demand
for optically clear products continues to grow in the world cosmetics market
and two new products recommended for clear stick formulations were also
introduced to the European market by Reheis at Cannes. They were Reach AZP-908
PG 30 and Reach 301 PG 30. The products are polyol adducts which are
presolubilised in propylene glycol. The polyol content helps to lower the
refractive index of the active and bring it closer to that of the base vehicle.
These actives are said to offer greater efficacy than conventional aluminum-zirconium
and aluminum chlorohydrate complexes and provide low whitening characteristics
to most formulas.
Despite
the undisputed efficacy of today's deodorant and antiperspirant actives
marketing departments and product formulators are still searching for
alternative methods and materials for reducing body odour and also for reducing
perspiration. A publication by Cosferm
[Ref. 2] describes the resident micro flora of the skin and suggests that
normally they exist in acceptable numbers in healthy equilibrium. This balance
is due in part to the free fatty acids released by the bacterial breakdown of
triglycerides having a limiting action on numbers but more importantly, to the
free sphingoid bases which show growth inhibitory activity against Gram-positive
bacteria, yeast and moulds. It is suggested that by topical application of
phytosphingosine the growth of undesirable micro-organisms will be inhibited
and this may result in a reduction of body odour. The following table shows the
concentration of phytosphingosine (g/L) required for complete growth inhibition
within one hour.
|
Micro-organism |
Undesirable phenomena |
Phytosphingosine (g.L) |
|
Staphylococcus aureus |
Atopic eczema,; infections; sores |
0.20 |
|
Corynebacterium xerosis |
Axillary odour |
0.16 |
|
Micrococcus luteus |
Axillary odour |
0.20 |
|
Propionibacterium acnes |
Acne, oily skin |
0.20 |
|
Escherichia coli |
Wound infections;, sores |
0.40 |
|
Pseudomonas aerigunosa |
Wound infections; sores |
0.10 |
Other
materials for which the suppliers claim deodorant properties include
octoglycerin from Schulke and Mayr under
the trade name Sensiva SC 50
which is said to inhibit the growth of odour-causing bacteria while at the same
time not affecting the natural skin flora and a lactate ester from Condea Chimica of Italy. Data shows
that di-C12-13 alkyl lactate has no inhibitory action against
bacteria but significantly reduces underarm odour. It is believed by the
suppliers that the absence of odour is due to the bacterial enzymes
preferentially breaking down the ester rather than the triglycerides of human
lipids. The material is suggested as a replacement for antimicrobial compounds
in deodorant sprays, lotions and creams, as an additive to antiperspirants to
enhance activity and, because it is compatible with surfactant systems, it is
suitable for shower gels and body washes making a deodorant claim.
Two
interesting physical means of reducing body odour are the use of a modified corn
starch and an acrylate crosspolymer. The modified corn starch is produced by National Starch and supplied under the
trade name Dry-Flo AF; it is said to be particularly suitable for use in powder
products, deodorants and antiperspirants. It absorbs body moisture and imparts
a dry lubricious feel to the skin. The mechanism may be contrasted with that
suggested by Dow Corning for
Polytrap whereby a macroporous cross-linked acrylate copolymer is applied to
the skin and this adsorbs the fatty acid components of human perspiration. The
macroporous copolymer possesses a pore diameter too small to allow penetration
by skin-resident bacteria, thereby retarding decomposition of the fatty acids.
The
effectiveness of copper and zinc salts in reducing body odour is now thought to
be because of their action in inhibiting the development of the bacterial
enzymes that cause malodour. Zincotrat is the trade name given by Vevy Europe to a solution of zinc
citrate in propylene glycol citrate which has astringent and deodorant
properties. Biostat (Variati & Co.),
is the copper salt of usnic acid, extracted from lichen in ethoxyglycol and
Evosina Na2 GP is the sodium salt in propylene glycol and both materials are
claimed to reduce body odour. Tegodeo JP 100 and Tegodeo HY 77 (Th Goldschmidt) are two differently
solubilised forms of zinc ricinoleate. Neither have bactericidal or fungicidal
properties but Goldschmidt states that the zinc salts chemically combine with
the bacterial decomposition products of perspiration, thus inhibiting odour
development. JP 100 is recommended for non-aerosol and predominantly
aqueous-based products such as roll-on deodorants and deodorant sticks whereas
HY77 is used in predominantly alcoholic products such as sprays.
The use of perfumes to cover body odour is as
old as civilisation; it was not until relatively recently that it was realised
that some of the constituents had an inhibitory effect and work by Blakeway
[Ref. 3] and others demonstrated the antimicrobial effects of various essential
oils. The use of aldehydes is also known to reduce apparent body odour and a
recent patent [Ref. 4] claims deodorant compositions containing at least two
aldehydes. It is interesting that many of the aldehydes meeting the criteria
cited in the patent occur naturally in the essential oils of aromatic plants. A
natural approach is to use Tricosulfan from Vevy Europe; this is a willow (Salix alba) bark extract free from coal tar or its adulterants.
Triclosan
is one of the longest established antimicrobial compounds with a proven effect
against odour-producing bacteria and is the benchmark against which most other
materials are tested. Exsymol
have incorporated Triclosan into nanospheres which may be added to any product
form containing a minimum of 60% water. After application the nanospheres are
said to liberate the active material over time, improving the effective life of
the deodorant while reducing any potential irritation from the triclosan.
Looking
through recent patent activity we find antiperspirant stick compositions
exhibiting improved wash-off performance [Ref. 5] and gelled or solid
antiperspirant deodorant compositions comprising a topically-active
antiperspirant compound crosslinked with a borate and a surfactant in a
substantially aqueous carrier [Ref. 6]. Until relatively recently roll-on and
stick type antiperspirant products were perceived as unpleasant in feel and
texture on application. The widespread use of silicone compounds has done much
to improve consumer acceptance of such products. A patent by Dow Corning Co.
[Ref. 7] describes spontaneously formed clear silicone microemulsions prepared
by combining water, a volatile cyclic methyl siloxane or volatile linear methyl
siloxane and a silicone polyether surfactant. The particle size of the siloxane
in the microemulsion is less than 100 nanometers and the composition is
therefore optically clear. Example antiperspirant formulations based on
aluminium chlorhydrate or aluminium-zirconium tetrachlorhydrex-gly are given.
The ratios of the three components of the basic system required to give clear
microemulsions vary considerably according to which methyl siloxane and
silicone polyether are used and a ternary phase diagram shows the different
ratios possible.
Despite
the obvious success of silicone compounds in improving the feel of
antiperspirant products other materials have also been examined and found
useful. Poly olefins such as polydecane are non-volatile hydrocarbons and it
has been found that their inclusion in an antiperspirant preparation can help
mask white deposits and improve the sensory feel of the product [Ref. 8]. Other
suitable named poly olefins are polybutene and polyisobutene and they are
preferably used as the main carrier in preparations at 30 - 60% by weight of
the composition. Other constituents may include volatile and non-volatile
silicones, liquid paraffins and fatty acid esters.
Patents
for deodorant compositions include one claiming superior resistance to
discoloration comprising an antibacterial zeolite having at least a portion of
its ion exchangeable ions substituted with ammonium ions and antibacterial
metal ions blended with a silicone [Ref. 9] and one for deodorant compositions
comprising inhibitors of odour-producing axillary bacterial exoenzymes
[Ref.10]. This last patent represents the new generation of non-antimicrobial
approaches to deodorant products whereby the bacterial exoenzymes responsible
for the production of steroidal axillary malodour are inhibited. Aryl sulfatase
and beta-glucuronidase are the primary bacterial exoenzymes responsible for
producing steroidal axillary odour and the inhibitors of these exoenzymes
include cupric hexametaphosphate, a gluco-lactone, EDTA, NTA, o-phenanthroline
and sodium sulfate or orthophosphate. An alternative embodiment of the
invention comprises inorganic acids, organic acids and water soluble metal
salts of fatty acids in combination with Zn++ compounds. The active
materials directly inhibit the bacterial exoenzymes responsible for the
production of steroidal axillary malodour rather than neutralising unpleasant
odours through chemical interaction and indirect inhibition of bacterial
growth. They may be dissolved or suspended in a cosmetic vehicle in the form of
a soap, lotion, fluid, cream, gel stick, powder or spray to provide a deodorant
composition to prevent axillary odour without disturbing the natural flora of
the axilla.
And
finally, from the Journal of the American Academy of Dermatology, a new study
on US Military Academy recruits, forced to go on daily 13 mile hikes, shows
that rubbing antiperspirant all over bare feet before setting out on a long
walk is a very effective way of preventing foot blisters....and presumably smelly feet.
Ref.
1. Dr Allan Rosenberg; Summit Research
Laboratories, private communication.
Ref.
2. Phytosphingosine for a
healthy skin flora; Cosmoferm, Delft, The Netherlands
Ref.
3 Blakeway, J. SPC 1986 (4):
201
Ref.
4 Patent 5795566: Robertet S.A.,
France. Issued: 18/08/98
Ref.
5 Patent 5733534: The Procter &
Gamble, USA. Issued 31/03/98
Ref.
6 Patent 5672340: Helene Curtis, Inc.
USA. Issued 30/09/97
Ref.
7 Patent EP 0 774 482 A2: Dow Corning
Co. Issued 14/11/96
Ref.
8 Patent EP 0 804 921 A1: Unilever
Plc. Application date 25/03/97
Ref.
9 Patent 5672340: Shinagawa Fuel Co.,
Ltd., Japan. Issued 3/03/98
Ref.10 Patent 5676937: Colgate-Palmolive Co. USA.
Issued 14/10/97