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Emollients, rheological additives: classification and application.
Antimicrobial used as preservatives, their merits and demerits

1st yr
Dept of pharmaceutics



• Emollients are topical treatments (treatments that are applied

directly to the skin)
They reduce water loss from the outer layer of skin
(epidermis) by covering it with a protective film.
Emollients are also sometimes known as moisturizers.
Emollients come in several different forms, including:

➢soap substitutes
➢bath oils
➢moisturising creams and ointments



• Emollients are moisturizing treatments applied directly to the

skin to soothe and hydrate it. They cover the skin with a
protective film to trap in moisture



Emollients may be medicated or non medicated.

Non-medicated topical emollients or moisturizers contain occlusive
agents(fat soluble emollients), and humectants( water soluble emollient).

• Emollients offer an occlusive barrier and they smooth flaky skin cells, to
make the skin look smoother. Some spread more easily than others. Esters
and oils can be used.

Emollients has three basic actions:
➢ Occlusion – Occlusive agents coat the skin, forming a physical barrier that

prevents the loss of water. EX- Petrolatum, waxes, oils, and silicones. They
can be uncomfortable on the skin, so they may be combined with an

➢ Humectants – include ingredients such as glycerin, urea and pyrolidine
carboxylic acid. They attract water from the atmosphere and from the
lower layers of skin to moisturize the surface of the skin. They can feel
sticky, so they will be combined with other elements like emollients.

➢ lubrication – adding slip or glide over the skin. 4


Some emollients contain specially medicated formulas that can be

used to treat skin conditions such as:
• eczema: a long-term (chronic) skin condition that causes the skin to

become reddened, dry, itchy and cracked
• psoriasis: a chronic non-infectious skin condition that causes red,

flaky patches of skin




1) Soap substitutes
Certain skin care products can remove your skin’s surface layer

of natural oils.
These include:
➢ soaps
➢ shampoos
➢ ordinary bubble baths
➢ shower gels
This can make your skin dry and can further aggrevate long-
term (chronic) skin conditions such as eczema.
Soap substitutes, such as aqueous cream or emulsifying
ointment, can be used instead of soap for hand washing and

Aqueous cream can also be used as a substitute for shaving


2) Emollient bath additives

Emollient bath additives can be added to a lukewarm bath to
help prevent the loss of moisture from your skin.

Bath additives can make surfaces slippery, so always use a non-

slip mat and be careful while bathing

Some bath oils include an antiseptic which can help prevent
infection. However, these products should only be used
occasionally unless the infection is recurrent or widespread.

Never use more than the recommended amount of bath
additive, If the concentration is too high, it may cause skin
irritation, particularly when used with antiseptic bath oils



Emollients are available as:
lotions – good for hairy or damaged areas of skin (such as

weeping eczema) as they are thin and spread easily, but they’re
not very moisturizing

sprays – good for hard-to-reach areas and for sore or infected
skin that shouldn’t be touched; quickly absorbed

creams – good for daytime use as they’re not very greasy and
are absorbed quickly

ointments – good for very dry, thickened skin and for night-
time use as they are greasy, thick and very moisturizing; they’re
usually free of preservatives so are suitable for sensitive skin, but
they shouldn’t be used on weeping eczema


bath oils and shower products



Emollients can be applied as often as you like to keep the skin
well moisturized and in good condition. Ideally, this should be
done at least three or four times a day.
It’s especially important to regularly apply an emollient to your
hands and face, as they’re exposed to the elements more than
any other part of your body.
Certain activities, such as swimming or gardening, can irritate
the skin. It may help to apply an emollient before doing these.
It’s a good idea to protect babies’ hands and cheeks with an
emollient before meal times to stop them getting sore from food
and drink.
Emollients are best applied after washing your hands, taking a

bath or showering because this is when the skin most needs
moisture. The emollient should be applied as soon as you have 9

patted your skin dry to ensure it is properly absorbed.


For eczema and psoriasis

Moisturizers and emollients are recommended for people with eczema and
psoriasis, at any age.

One study that looked at the feasibility of skin barrier treatment from birth
concluded: “The results of this trial demonstrate that emollient therapy from
birth represents a feasible, safe, and effective approach for atopic dermatitis
prevention. If confirmed in larger trials, emollient therapy from birth would
be a simple and low-cost intervention that could reduce the global burden of
allergic diseases.”

People with eczema or psoriasis can find soap too drying to the skin , Many
bar soaps, liquid soaps, and cleansers and perfume products can irritate the
skin. Emollient soaps substitutes do not foam but they clean the hands and
skin, They can be applied before washing or in the water 10


Rheological additives



• Today’s successful cosmetics products need the right
rheological properties and the correct choice of rheological
additive enhances the product in production, storage stability
and application.

• Rheological additives for aqueous and non-aqueous
formulations are valuable and proven tools for you to use,
a. Personal care
b. skin care
c. sun care
d. decorative cosmetics

• all can benefit from rheological additives 12


• Rheology is the science of flow.

• Every time a lotion is poured, a cream squeezed from a tube or a
lipstick applied, rheology is involved.

• Even when products are at rest, it plays an important part in
controlling stability and suspension.

• understanding a formulation’s rheological needs enables you to
create the best possible products.

• The rheology of a system is described in terms of its viscosity.
Viscosity is the resistance to flow and defined as:
VISCOSITY= shear stress/shear rate



• Shear stress is the force per unit area applied and shear rate is the resulting
velocity gradient.

• Cosmetics experience shear rates varying from 0.001 s-1, from gravitational
forces to over 20,000 s-1, when a cream is spread or an aerosol antiperspirant

• The way the viscosity changes at varying shear rates greatly influences the
overall product stability and performance.

• A material which maintains a constant viscosity, regardless of shear rate,
has Newtonian flow.

• Dilatants flow is a form where viscosity increases with shear.

• pseudo plastic flow, also known as shear thinning behavior, and typical of
many commercial systems, is when viscosity decreases with increasing shear

• Viscosity can be temperature dependent, Correct choice of rheological
additive allows you to create the ideal flow characteristics and also achieve
thermostable rheology.


• Aqueous-Phase Additives

➢ Rheoluxe Associate Thickeners
➢ Hectorite
➢ Bentone hydrophilic Clays

• Non-Aqueous-Phase Additives

➢Bentone organophilic Clays
➢Bentone GEL
➢Thixcin R Rheological Additive




1) Rheoluxe Associative Thickeners

• The rheoluxe family of rheology modifiers are non-ionic
polymeric thickeners designed specifically for the personal
care market.

• Rheoluxe consists of urethane based and Polyether Polyol
based associative thickeners with superior performance in
difficult systems such as those containing high salt levels or
with extremes in pH.

• Due to its structure, Rheoluxe is soluble in water, but
associates with lipophilic materials to build viscosity.



• Hectorite is a unique swelling clay offering several advantages.

• Hectorite’s special properties are:
➢lower iron content
➢lighter colour
➢higher swelling capacity
➢ greater gel strength
➢platelet shape and large surface area



• Hectorite is able to form strong, stable viscous

• Hectorite is a very effective thickener of water.

• Because of this and its other exceptional
properties, it forms the basis as rheological
additives in cosmetics.




BENTONE MA, EW, and LT rheological additives provide thixotropy to
the aqueous phase.

• BENTONE MA and EW additives form gels by producing an open, 3-
dimensional network of the individual clay platelets.

• The two products are stable across the range pH 6-11 and offer good
tolerance to electrolytes.

• BENTONE LT forms a similar network, but it is strengthened by the
presence of a special cellulose, greatly enhancing stability and
thickening characteristics.

• BENTONE LT is stable across a broader range, pH 3-11, and is also the
least electrolyte- sensitive product.

• BENTONE MA and EW are in compliance with ECOCERT , The
ecological and organic cosmetics standards. 19


• Surfactants can influence the rheological behaviour of hydrophilic clays.

• Non-ionic surfactants, if they are highly ethoxylated, can adsorb onto the
clay surface , This rarely causes problems either in flow control or activity of
the formulation.

• Anionic surfactants can act as dispersing agents and weaken the gel
structure , Alternatives that eliminate or minimise any problems can
normally be found.

• however, cationic surfactants interact strongly and should be avoided.

• The benefits gained are:
• thermostable viscosity control
• thixotropic flow
• emulsion stabilisation
• silky skin feel



Non aqueous phase additives
1) BENTONE organophilic Clays

• Hectorite is now reacted with special vegetable quaternary ammonium salts to
produce organoclays able to thicken and gel organic liquids.

• The correct choice of bentone additive is determined largely by the polarity of the
system to be thickened.



• BENTONE additives need to be efficiently dispersed
using high-shear equipment and then to be activated
with the optimum level of a chemical activator, such as
propylene carbonate.

• BENTONE organoclays form thixotropic gels by
developing hydrogen bond bridges between the edges
of adjacent platelets




• BENTONE GEL additives are optimally dispersed and activated
pre- dispersions .

Benefits include:
• optimally dispersed
• high-shear dispersion not necessary
• no polar activation required
• easy to handle and use
• can be added at any appropriate and convenient stage in


• A wide range of gels made from various cosmetics oils, esters

and solvents are available.


• The use of a BENTONE GEL enables you, the
formulator, to achieve the maximum efficiency from
the organoclay without the need for careful
shearing and activation.

• On the production scale, time is saved and the
highest degree of reproducibility attained, leading to
potential cost savings



THIXCIN R Rheological Additive
• For the highest degree of thixotropy in aliphatic liquids, Thixcin R

additive is the product to use.

• In addition to its effective rheological properties, it gives water
repellency, stabilizes emulsions and acts as a stiffening agent in lipsticks
and ointments.

• It can also be used as a dry binder in pressed powder systems (Where
high- temperature resistance is needed, BENTONE or BENTONE GEL
additives are recommended).

• Thixcin R is a castor oil derivative , It requires temperature-controlled
activation within the range 55-60°C (130-140°F) and high-shear mixing
to develop its full structure.

• Thixcin R is in compliance with Ecocert, The ecological and organic

cosmetics standards.



➢ Stick products (lipstick and antiperspirant)
• maintain homogeneity in molten and setting stages
• increase high-temperature integrity
• eliminate oil migration

• reduce “creasing” around lips and eyes

➢ Mascara
• improve film-build
• increase water-resistance
• eliminate oil migration 26


• elevate drop-point temperature of water-in-oil creams
• eliminate syneresis
• improve emulsion stability
• enable cold-process emulsification
• create novel viscosity effects

➢ UV Sunscreen
• eliminate ultrafine titanium di oxide skin-whitening problems
• enhance sun protection factor (SPF)
• optimise use of sunscreen actives
• reduce separation and settlement

➢ Antiperspirant Aerosols
• uniform distribution of active ingredients
• soft and dry skin feel
• significant less whitening
• reduced separation and settlement 21



Antimicrobials as preservatives
• Definition:
The agents which is active against gram positive and gram
negative micro organisms that causes degradation of
pharmaceutical preparation

These agents are active in small inclusion levels

They act by cellwall inhibition , protein synthesis inhibition , DNA
and RNA synthesis inhibition



• Differ greatly in ability to act against different microorganism.
• Some are Narrow spectrum.
• Some are Broad spectrum.
• Some act against viruses, bacterial spores,or fungi



An antimicrobial preservatives must be
• Less toxic.
• Broader antimicrobial spectrum.
• Cidal effect.
• Not only effective against vegetative cells but also

against spores.
• Stable to heat and storage
• Chemically compatible.
• Reasonable cost.
• Acceptable taste,odour and color.
• Available in aqueous phase at effective level

• Should be in unionized state to penetrate bacteria. 30

• Must no bind to other components of emulsion.


Commonly used preservatives
Ingestible & Topical
• Methyl, ethyl, propyl and butyl Parabens
• Sorbic acid
• Na, K & Ca Sorbate
• Benzoic acid
• Na, K & Ca Benzoate
• Sodium metabisulfite
• Propylene glycol (15-30%)
• Flavors w/ benzaldehyde

Topical Only
Formaldehyde donors
Essential Oils

Mercury compounds


• Parabens are among the most commonly used preservatives.
• They are relatively active against a broad spectrum of

• The methyl ester is most effective against bacteria and molds

while the ethyl, propyl and butyl esters are more active
against yeast and molds.

• Parabens are more effective against gram negative than gram
positive organisms.



Chelating Agents as Preservative
• Alkaline earth metals such as Ca+ and Mg+ are important for

the stabilization of the outer membrane of cellular organisms.
• Chelating agents sequester these ions. This contributes to the

partial solubilization of the cell membrane which allow
preservatives a pathway into the cell.

• EDTA is a typical chelating agent used in formulations.



Ingredients That Enhance

• Efficacy
• Solutes (salts & high concentration of sugars)
• Esters
• Cationic and anionic surfactants
• Humectants (glycerin, propylene glycol)
• Phenolic antioxidants (BHT)
• Chelating agents (EDTA)
• Fragrances
• Low water activity



• Antimicrobial presevative in cosmetics and personal care

products help, prevent the growth of moulds, yeast, and

• Protect the products from spoilage or contamination

• Preservative act as decomposition preventer by actively
working to prevent microbial growth in products ranging from
sunscreens, lotions, shampoos, cleansers, toothpaste etc

• Antioxidant preservatives help to prevent the spoiling of
products by suppressing the reaction that can occur when
some ingredients in a cosmetic combine with oxygen in 35
presence of light, heat, and some metals


• Skin irritation
• Hypersensitivity reaction
• Rashes
• Skin disorders
• Long term use may lead to skin cancer



Thank you