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Skin Exfoliation 

by Diana L.Howard Ph.D. 

The International Dermal Institute 

Published as Sloughing Off in Les Nouvelles Esthetiques September 2003 
Introduction 

With so much attention focused on addressing the needs of both maturing and 
prematurely aged skin and the continual interest in using ingredient complexes such as 
hydroxy acids, retinol and other chemical and physical exfoliants, we are often asked at 
The International Dermal Institute to explain how these different ingredients work on the 
skin. 

How does desquamation work? We know from our research that epidermal cells adhere to 
each other on the top, sides and bottoms of the cells via calcium dependent desmosomes. 
As the cells move upward from the deeper layers of the epidermis to the outermost layers 
of the stratum corneum, the desmosome attachments become weaker. This weakening 
action is accelerated by enzymes, found only in skin and hair follicles. These enzymes break 
the bonds of the desmosomes and free the cells to slough off. 

What controls this desquamation process? While the exact mechanism is unknown, it is 
believed that cells are programmed when they are young and residing in the lower layers 
of the epidermis; each cell has an internal clock that ensures the cell is linked for a certain 
period of time and then cell cohesion decreases allowing the cells to slough off. 
Interestingly, the enzyme responsible for weakening the bonds is inactive in the skin until 
activated by another enzyme. What controls this activation process is not readily 
understood. 

The complex process known as keratinization, commences with the birth of a new 
daughter cell at the basal cell layer (stratum germinativum) and its progression upward 
until it is shed as a stratum corneum corneocyte. This normally takes about four weeks, 
however, it can take as much as seventy-five days depending on age and the condition of 
the skin. As to be expected, younger skin is more efficient at this process of desquamation 
which stimulates the growth of newer cells at a deeper level. As we age the glue-like 
intercellular cement holding the cells together becomes denser, causing a build up in the 
layers of cells; cell sloughing becomes more difficult resulting in a skin that appears dull, 
thicker and with less tone. This may be exacerbated by environmental factors (exposure to 
sunlight), hormonal influences (androgens, estrogens, and epidermal growth factor) and 
deficiencies in various vitamins (A & D). With all of these influences effecting the 
desquamation process it is apparent why exfoliation is so important to the skin. Removing 
this build up of dead, damaged skin cells stimulates the regeneration of new cells 
improving the skin's appearance, feel and texture. 

As professional skin therapists and consumers we have several means to affect the 
desquamation process. We can select to use mechanical exfoliants that help eliminate 
surface stratum corneum cells. Or we can choose chemical means, such as hydroxy acids 
to aid in exfoliation and stimulate cell renewal; in addition to hydroxy acids , enzymes from 
papaya (Papain) and pineapple (Bromelain) can be used along with Vitamin A ( Retinol) 
that accelerates cell turnover. More recent studies have demonstrated that enzymes from 
Bacillus ferment (a bacteria produced enzyme) act as proteolytic agents digesting keratin 
protein and assisting in the exfoliation process. (For the purpose of this discussion we will 
only look at ingredients that affect skin exfoliation and not mechanical devices such as 
microdermabrasion.) 

Whether you select mechanical or chemical means of exfoliation, each can be of benefit 
and provide substantial improvement for dry skin, acne and photodamaged skin 
depending on the technique and substance used. Lets look at how these different 



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methods of exfoliation affect the skin. 

Mechanical exfoliation employs the use of either a tool (i.e. a brush, sponge) or substrate 
(i.e. Corn Cob Meal, Rice Bran, Date Seed Powder, Oatmeal) that loosens and reduces the 
outer corneocytes that comprise the stratum disjunctum layer when friction and abrasion 
are applied. Obviously results will vary depending on the amount of friction and the nature 
of the abrasive used. It is important to note that excessive abrasion can result in skin 
irritation so one must be careful in the type of abrasive used; for this reason The 
International Dermal Institute only recommends the use of abrasives that do not result in 
irritation, hence, we do not recommend the use of crushed fruit pits, shells or similar 
damaging substrates. 

Chemical exfoliation utilizes chemicals, such as hydroxy acids, (i.e. Lactic Acid, Salicylic 
Acid, Glycolic Acid), Retinol (i.e. Vitamin A) and enzymes (i.e. Papain, Bromelain and 
protease enzymes from Bacillus microbes). While the precise mechanism of action is still 
being debated, there are those that believe that alpha hydroxy acids (AHAs; i.e. Lactic 
Acid, Glycolic Acid, Malic Acid) do not exfoliate the skin in the same conventional way 
that mechanical exfoliants or beta hydroxy acids (BHAs; i.e. Salicylic Acid) do. It is thought 
that AHAs primarily affect the skin by normalizing eel! turnover in the epidermis; this 
stimulates the formation of normal healthy skin, which includes a sloughing of the stratum 
corneum, a decreased formation of dry scales on the skins surface and stimulation of the 
cell cycle. While this is indeed plausible, there are some researchers that believe the 
mechanism of action for AHAs cannot be tied solely to stimulation of the skin as measured 
by traditional cell renewal techniques. Studies on cell cohesion and skin pH changes 
indicate that keratin bonds may be affected and that low pH levels associated with active 
AHA solutions may dissolve the desmosome protein linkages causing a burst in skin 
exfoliation. It is often said that AHAs affect the skin from the inside out because of the 
suggestion that they influence corneocyte cohesion at the lower layers of the Stratum 
corneum. The result is a thinner stratum corneum which is more flexible and compact, 
reflects more light and overall gives the skin a more youthful appearance. . 

While it is thought that both glycolic acid and lactic acid affect the skin layers in the same 
manner as described above, it should be noted that there are additional beneficial effects 
unique to lactic acid. These include an increase in dermal Glycosaminoglycans (GAGs- 
natural moisturizers), an increase in ceramides (epidermal barrier lipids) and improved 
water barrier properties. Glycolic acid does however, share with lactic acid the beneficial 
affect of stimulating collagen synthesis. It has been speculated that this latter affect may 
be the result of irritation resulting in a natural stimulation of new collagen. Surprisingly, there 
are no published reports that the BHA, salicylic acid, stimulates the formation of collagen 
like the AHAs. 



Unlike Lactic Acid, Salicylic Acid does not hydrate the skin nor does it help to normalize 
epidermal anatomy or physiology. Salicylic Acid, primarily a keratolytic agent, dissolves the 
stratum corneum (SC) layer-by-layer from the outside in, resulting in a thinning of the SC. It 
has been demonstrated to affect hyperpigmentation but only when used at very high 
concentrations (50%). And unlike AHAs, salicylic acid affects the arachidonic acid cascade 
and exhibits anti-inflammatory properties, making Salicylic acid products seem less irritating 
than glycolic acid, even though they are more powerful. The anti-inflammatory effects of 
salicylic acid make it a preferred option for clients with acne and rosacea. 

Salicylic acid also differs from AHAs due to its lipophilic nature which enables it to penetrate 
sebaceous substances in the hair follicle and exfoliate the pores. AHAs being water soluble 
are not as effective. In studies comparing a 2% salicylic acid solution vs. a 8% glycolic acid 
solution, the salicylic acid significantly decreased the density of microcomedones, 
whereas, the glycolic acid solution did not. Because Salicylic acid has a much stronger 



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comedolytic effect than AHAs on the skin I would highly recommend salicylic acid 
containing products when treating clients with acne. 

While the precise mechanism of action of hydroxy acids is still open to debate, there is a 
general consensus that exfoliating the outermost layers of the stratum corneum (the 
stratum disjunctum) results in improved skin texture, and a reduction in fine lines and 
hyperpigmentation. Recent studies have demonstrated that a 5% Lactic acid solution not 
only stimulated stratum corneum sloughing but increased skin hydration and helped to 
reduce hyperpigmentation. Studies done by Walter Smith Ph.D comparing efficacy of a 4% 
Glycolic acid solution vs a 4% Lactic Acid solution (both at a pH of 3) indicate that Lactic 
acid was not only less irritating but slightly more effective than glycolic acid in stimulating 
cell turnover. Interestingly, a 4% solution of Salicylic acid was superior to both of the alpha 
hydroxy acids. 

One final note on the use of alpha hydroxy acids. For safe use of glycolic and lactic acid it 
is advisable to follow the CIR suggestions (endorsed by EMDA) that indicate consumers 
should not use products above 10% or below a pH of 3.5; for professional use, the limits are 
extended to 30% and the lowest advisable pH is 3.0. In addition, if you are prescribing 
hydroxy acid products to your clients it is imperative that you advise them that the use of 
hydroxy acids can make skin more sensitive to sunlight. Always recommend they use at 
least a SPF 1 5. It is only a matter of time until a sun alert warning will be required for all AHA 
products. 

In recent years, Retinol [Vitamin A) has been included in exfoliation formulas because the 
skin can convert Retinol to Retinoic Acid, a potent skin exfoliation agent and antiaging 
agent. Retinol has been shown to improve the visible signs of photoaging as well as normal 
chronological aging when used on a daily basis. Studies conducted by Drs. Kang and 
Voorhees at the University of Michigan department of dermatology indicate that retinol 
mimicked the activity of retinoic acid in stimulating a thickening of the epidermis but 
without the irritation often seen with retinoic acid. Further studies also showed that retinol 
slowed collagen degradation when skin was exposed to sunlight, an observation attributed 
to the ability of retinol to inhibit enzymes such as collagenase that are responsible for 
degradation of collagen. 

Biological enzymes such as Papain (from papaya] and Bromelain (from pineapple) 
stimulate exfoliation by digesting intercorneocyte cohesion chemically; these proteolytic 
enzymes decompose proteins into smaller fragments causing a softening effect to the skin 
and a sloughing of corneocytes. Unlike AHAs their activity is not pH dependent but is 
activated by water and limited in the amount of exfoliation that can be achieved. 

Recently studies on still another enzyme, the protease enzyme from the microorganism 
Bacillus subtilis, have demonstrated that this enzyme extract is a beneficial keratolytic 
agent that helps eliminate desquamating corneocytes when applied topically. 

Other ingredients may be used to assist in exfoliation including rice extract and rice bran. 
While the nutritional value of rice (Oryza Sativa) is well known, less obvious are the 
medicinal and cosmetic applications of this historical grain. Rice seeds and bran have 
been used for thousands of years to relieve inflammation associated with skin diseases and 
for cleansing and softening the skin. Traditionally women in Japan have rubbed Rice Bran 
on their face keep to skin smooth and bright. Not limited to a beauty regimen of the upper 
class, women rice farmers used the water left over from washing white rice to bathe in and 
wash their face for the same reasons-smooth, luminous looking skin. What do we attribute 
these benefits to? Chemical analysis of Rice Bran (the outer layer on brown rice) indicates it 
is a rich source of biologically active agents that are beneficial to the skin. These include 
Phytic Acid, gamma oryzanol and other important plant actives. Studies have shown that 
Rice Bran contains 10% Phytic Acid (AKA myo-inositol, a B complex vitamin) which chelates 
or binds calcium ions, helping to loosen cell cohesion and promote corneocyte sloughing. 



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Phytic Acid also chelates copper, thereby, inhibiting tyrosinase in melanogenesis and 
controlling hyperpigmentation. It also increases peripheral blood tlow to the skin. Gamma 
Oryzanol, a derivative of Vitamin B, is also known as a Ferulic Acid Ester. It provides 
enhanced antioxidant protection when complexed with amino acids found in rice extract 
and rice starch. It softens skin and provides anti-itch properties. In addition, Oryzanol may 
impede melanogenesis by inhibiting tyrosinase. Whats more, Rice bran contains 
Tocopherols (antioxidant Vitamin E that protect against free radicals; Proanthocyanidins 
(anti-enzyme inhibitors of collagenase, elastase and hyaluronidase) and other Enzymes (i.e. 
Super oxide dismutase, SOD). 

Regardless of which type of exfoliant you select to use on your client, you should always 
complete a Consultation card to assess what products they may be using at home, if they 
are using any prescription medications that will seriously alter their skin physiology and the 
frequency of use of these products. There is a valid concern that clients at home may be 
over-exfoliating their skin. In their quest to achieve that radiant, healthy looking 
complexion, consumers often will double up on their at-home exfoliation treatments and 
even use exfoliants from different manufacturers on alternate days. Unfortunately 
consumers tend to subscribe to the erroneous belief that "if a little is good, more must be 
better". With repeated over-exfoliation, the inevitable result will be to diminish the skin's 
natural barrier function thereby contributing to a potentially sensitized skin condition and 
ultimately dehydration. Tell-tale signs of over-exfoliated skin include: noticeable 
dehydration, patchy areas of dryness, skin tautness, a transparent looking epidermis, 
redness or couperose condition, broken capillaries, itchiness, increased sensitivity, 
inflammatory acne and irritation. 

As we focus on the benefits of exfoliation, we will see more refined methods of assisting with 
the desquamating of corneocytes. Our goal as scientists and professional skin therapists at 
The International Dermal Institute is to continue to research new ingredient complexes that 
help us to achieve the benefits of exfoliation while maintaining optimum skin fitness and 
health. 



Before You Exfoliate: 

• The Client Consultation System is 
a very useful component of every 
treatment, and is especially 
important whenever any form of 
exfoliation is to be performed. All 
clients should complete a 
Consultation Card prior to product 
application. 

• If the client is using Retin-A, 
Renova, Adapalene or any other 
exfoliating product, they must 
discontinue use at least two weeks 
before undergoing any exfoliation. 

• Clients who are taking 
Accutane, or have taken 
Accutane within the past six 
months, should not receive any 
form of exfoliation treatments. 

• Do not perform any type of 
exfoliation on sunburned or 



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irritated skin, or on skin that has 
been waxed within the past 24 
hours. 

• Always recommend that the 
client use a sunscreen with a 
minimum SPF 1 5 whenever going 
outdoors. 



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