AHAs vs. BHA
There are two primary topical ways to exfoliate skin,
either with alpha hydroxy acids (AHAs), or with beta hydroxy
acid (BHA). There is only one BHA (beta hydroxy acid)
and that is salicylic acid, but there are a variety of
AHAs. The five major types of AHAs that show up in skin-care
products are glycolic, lactic, malic, citric, and tartaric
acids. Of these, the most commonly used and most effective
AHAs are glycolic and lactic acids. Both of these have
the ability to penetrate the skin, plus they have the
most accumulated research on their functionality and benefit
for skin.
What glycolic, lactic, and salicylic acids both do is
"unglue" the outer layer of dead skin cells,
allowing healthier cells to come to the surface. Removing
this dead layer can improve skin texture and color, unclog
pores, and allow moisturizers to be better absorbed by
the skin. Both AHAs and BHA affect the top layers of skin,
and they help to improve the appearance of sun-damaged,
dry, and/or thickened skin. Sun damage in particular causes
the top layer of skin to become thicker, creating a dull,
rough appearance on the surface of skin (Sources: Archives
of Dermatologic Research, June 1997, pages 404–409; Dermatologic
Surgery, May 1998, pages 573–577). There is even research
showing AHAs can generate collagen production (Sources:
Experimental Dermatology, April 2003, (Supplemental),
pages 57-63 and Dermatologic Surgery, May 2001, page 429.)
Because AHAs and BHA work through chemical processes,
they can penetrate the skin and produce better results
than cosmetic scrubs, which work only on the exposed surface
of the skin. And, there is no risk that AHAs and BHA will
cause you to lose too much skin. Technically, there is
a drop-off rate, meaning the AHA and BHA will exfoliate
just the dead or damaged surface skin and leave the healthy
skin alone. This is the main reason why you will see a
drop-off in performance when using an AHA or BHA product.
The dramatic results in the beginning of usage (when the
thickened, discolored layers of skin are being removed)
seem much more impressive than the results from continued
use. This is to be expected, and it is important to note
that continued use of an AHA or BHA product is required
in order to maintain skin’s smooth, even-toned, healthy
appearance.
The primary difference between AHAs and BHA is that AHAs
are water-soluble, while BHA is lipid-(oil) soluble. This
unique property of BHA allows it to penetrate the oil
in the pores and exfoliate accumulated skin cells inside
the oil gland that can clog pores. BHA is best used where
blackheads and blemishes are the issue, and AHAs are best
for sun-damaged, thickened, dry skin where breakouts are
not a problem (Source: Global Cosmetic Industry, November
2000, pages 56–57).
pH Sensitive AHA and BHA
AHAs work best at concentrations of 5% to 10% with a pH
of 3 to 4, and their effectiveness diminishes as you go
above a pH of 4.5. BHA works best at concentrations of
between 1% and 2%, and at an optimal pH of 3, diminishing
in effectiveness as you go past a pH of 4. Both AHAs and
BHA lose their effectiveness as a product's pH goes up
or the concentration of the ingredient goes down. (Source:
Cosmetic Dermatology, October 2001, pages 15–18).
If the cosmetics industry isn't forthcoming about the
necessary percentages and pH for a BHA or AHA product
(and most companies aren't), how can you tell if it provides
decent or effective exfoliation? Consumers can't, not
unless they are shopping with pH measuring paper in hand,
which is exactly how I rate exfoliants when I review products
for my book, newsletter, or Beauty Bulletin. As a general
rule, it is best if the AHA ingredient is either second
or third on the ingredient list, making it likely that
the product contains a 5% or higher concentration of AHAs.
For salicylic acid, because only a 2% to 0.5% concentration
is required, it is fine if this ingredient is located
toward the middle or end of the ingredient list.
It is interesting to note that at any pH, AHAs provide
the added benefit of helping to keep water in the skin
at the same time that exfoliation is taking place. This
is due to the way they affect skin cells adding increased
protection. AHAs can also increase the production of ceramides
in the skin, which help keep it moist and healthy (Source:
Dry Skin and Moisturizers Chemistry and Function, edited
by Marie Loden and Howard Maibach, 2000, page 237).
While BHA penetrates deeper into the pore than AHAs,
it can be less irritating than AHAs. This is due to BHA's
relation to aspirin. Aspirin (acetylsalicylic acid) has
anti-inflammatory properties and BHA, salicylic acid,
is derived from aspirin and on the skin, retains some
of its same anti-inflammatory benefits.
AHA and BHA products can definitely smooth the skin,
fade signs of sun damage, correct uneven skin tone, improve
texture, unclog pores, and give the appearance of plumper,
firmer skin (because more healthy skin cells are now on
the surface). Unfortunately, they have no residual effect—when
you stop using them the skin will go back to the condition
it was in before you started.
AHA Confusion
There are AHA sound-alikes, including sugarcane extract,
mixed fruit acids, fruit extracts, milk extract, and citrus
extract. You may think you've purchased a more natural
AHA product when you see these less technical names, but
that isn't the case. Although glycolic acid is derived
from sugarcane, and lactic acid from milk, that doesn't
mean sugarcane extract or milk extract are the same as
glycolic or lactic acid, yet they do share these acid’s
water-binding properties, in much the same way as salicylic
acid share’s the anti-inflammatory properties of its relation,
aspirin.
Unless you see glycolic, lactic, malic, tartaric, or
citric acid on the ingredient list, it's all too vague
and meaningless, making it impossible to determine what
you are really buying. My advice is to be very suspicious
of any product that claims an association with AHAs but
contains a variety of sound-alike ingredients.
BHA Confusion
Products boasting that they contain a natural source of
salicylic acid (BHA) usually add willow bark. Willow bark
contains salicin, a substance that when taken orally is
converted by the digestion process to salicylic acid.
That means the process of converting willow bark to salicylic
acid requires the presence of enzymes to turn the salicin
into salicylic acid. The likelihood that willow bark in
the tiny amount used in cosmetics can mimic the effectiveness
of salicylic acid on skin is in all likelihood impossible.
However, willow bark may indeed have some anti-inflammatory
benefits for skin because, in this form, it appears to
retain more of its aspirin-like composition.
What About Higher Concentrations of AHAs?
Removing the outer layer of skin can be taken too far,
and many cosmetic dermatologists and researchers worry
that the increased irritation and exfoliation caused by
higher concentrations (above 10%) of AHAs may be too much
for skin. Without more evidence showing a benefit from
higher concentrations, I feel that you can achieve great
results without any unwanted side effects. Further, the
positive results women and men perceive with higher concentrations
of AHAs may come from the swelling and edema they cause.
That may diminish the appearance of wrinkles and make
the skin feel smoother, but it is most likely not best
for the long-term health of the skin due to the increased
amount of constant irritation.
Polyhydroxy Acids
The search for an effective form of AHA or an extra ingredient
that can enhance performance and reduce irritation has
been a popular topic of discussion among cosmetics formulators.
Gluconolactone is a type of polyhydroxy acid that NeoStrata
believes serves both ends: It is supposed to be just as
effective as AHAs but also less irritating.
Gluconolactone (PHA) is similar to AHAs. The significant
difference between the two is that gluconolactone has
a larger molecular structure, which limits its penetration
into the skin, resulting in a reduction of irritating
side effects in some skin types. So is gluconolactone
better for your skin than AHAs? Research indicates that
AHA and PHA perform identically with AHA having a slight
edge for improving the appearance of skin and PHA having
less risk of irritation (Source: Cutis, February 2003,
(2 Supplemental), pages14-17).
Retinoids (Retin-A, Differin, and Tazorac)
Let me make it perfectly clear that retinoids are not
exfoliants, though many people think that's what they
do. Retinoids are a general term referring to a vast range
of ingredients derived from vitamin A. Prescription-only,
topically applied retinoids are significant for skin because
they can positively affect the way cells are formed deep
in the dermis.
If you have sun-damaged, dry, wrinkled, or acne-prone
skin, you should become familiar with the names Retin-A,
Renova, Differin, Avita, and Tazorac, which all contain
different forms of retinoids. The active ingredient in
Retin-A, Avita, and Renova is tretinoin, Differin uses
adapalene, and Tazorac uses tazorotene. In fact, both
Renova and Tazorac have been approved by the FDA for the
treatment of wrinkles (Sources: Dermatologic Surgery,
June 2004, pages 864-866; Archives of Dermatology, November
2002, pages 1486-1493; Clinical and Experimental Dermatology,
October 2001, pages 613–618; and www.fda.gov).
Exfoliants such as AHAs and BHA primarily affect the
surface of the skin (epidermis) or the lining of the pore
by actually ungluing or dissolving layers of skin cells.
In contrast, retinoids affects the lower layers of skin
(dermis), where new skin cells are produced. Retinoids
actually communicate with a skin cell as it is being formed,
telling it to develop normally instead of developing as
a sun-damaged or genetically malformed skin cell.
Why the confusion about the effect retinoids can have
on the skin? Primarily it's due to the fact that products
containing retinoids can cause irritation and inflammation,
resulting in the skin becoming flaky and dry. This flaking
and dryness is not exfoliation, nor is it a desirable
or advantageous result. If retinoids cause your skin to
be consistently dry and flaky, it is a problem and you
should probably avoid products that contain it or reduce
how often you use them.
Despite the valuable effect retinoids can have for skin,
don't expect retinoids to erase wrinkles because they
are not a wrinkle cure. However, if skin cells can be
produced with a healthier form and shape, the skin's surface
will have a smoother appearance, skin cells will do their
job of turning over in a more normal fashion, the protective
outer layer of skin will remain intact, enhancing the
skin's healing response, and on and on. In essence, the
skin will behave and look the way it did (to some extent)
before it was damaged by the sun.
Regardless of these positive effects, retinoids will
be useless, and the skin will be prone to more damage,
if you do not wear a sunscreen as well. Not a wrinkle
cream in the world, even one approved by the FDA, can
have positive results if you don't use an effective sunscreen;
without that, you are just adding to damage you already
have accumulated.
What retinoids, AHA, and BHA products have in common
is that once you stop using them, your skin will revert
to the way it was before. These products will not produce
permanent change. The smooth exterior lasts only as long
as you use them. But used together long-term, they are
a formidable weapon in the battle against wrinkles and
blemishes.