ALPHA HYDROXY ACIDS, how they help

[lauryn]

What Are Alpha Hydroxy Acids and How Do They Work?

Alpha-hydroxy acids are naturally occurring acids, derived from the sugars in particular plants. Some examples are Glycolic Acid (Sugar Cane), Lactic Acid (Milk), Tartaric Acid (Grapes), Citric Acid (Citrus Fruits), Malic Acid (Apples), and Mandelic Acid (Bitter Almonds). These acids work at the very base of the stratum corneum, dissolving the cement that holds dead skin cells together. This increases cell turnover and influences the structure of new stratum corneum being made. This results in skin that is more flexible, more smooth, and more even in tone. At greater concentrations (12%-20%), deeper dermal effects, such as higher amounts of mucopolysaccharides and collagen and increased skin thickness, are observed. Eventually, alpha hydroxy acids will produce skin that is softer, smoother, less wrinkled, less dehydrated, and more even in skin tone.

[lauryn]

The Myths

There is a lot of information out about alpha hydroxy acids, however, much of it is misleading or simply untrue. Separating the truth from the rumors can be nearly impossible for the average person. Here are a few of the common myths surrounding alpha hydroxy acids.

Myth #1: Alpha hydroxy acids thin the skin. Actually, it is quite the opposite. AHA's at greater bioavailability appear to have dermal affects that influence the formation of collagen. Alpha hydroxy acids, on topical application to photoaged skin, have been shown to substantially increase skin thickness. Skin biopsies revealed increased synthesis of mucopolysaccharides and collagen as well.

Myth #2: Alpha hydroxy acids cause sun sensitivity. Used correctly, alpha hydroxy acids do not increase sun sensitivity. Sun sensitivity occurs when skin is irritated and inflammation occurs. Those with very fair coloring are especially susceptible to this since their skin tends to be more sensitive. Avoiding high concentrations (15% or more) or products with pH's lower than 3 can help avoid this. For those with more sensitive skin, use of a non-irritating AHA such as mandelic acid, lactic acid, or gluconolactone (gluconic acid) will help one avoid this problem.

Myth #3: Use of Salicylic Acid or a Mechanical Scrub will produce identical exfoliation benefits. Salicylic acid works from the uppermost layer of the skin, dissolving skin layer by layer. Mechanical Scrubs work only to remove already loosened skin cells on the upper layer of skin. Alpha hydroxy acids work at the lowermost levels of the stratum corneum. It appears that AHA's modulate new stratum corneum formation by weakening the bonds between corneocytes (a type of skin cell) at the lowest levels of the stratum corneum. This activity on the formation encourages a smoother, flatter cell layout in the stratum corneum. This new distribution of cells is particularly useful for prepping skin for peels.

Myth #4: Anti-Wrinkle benefits of AHA's are due to their exfoliating nature. While it is true that the exfoliating nature of AHA's contribute to softer skin that is more even in tone, the clinical effects of AHA's in modifying wrinkles and photoaging are due to increased skin thickness and new collagen formation.

Myth #5: When using AHA's, the skin looks smoother because the skin is swollen from inflammation. Improvements in wrinkles are not due to inflammation or any edema formation (excess accumulation of fluid in tissue spaces). Examination of biopsied skin specimens before and after treatment with AHA's have confirmed that skin plumpness and other beneficial effects are sustained long after discontinuation of topical treatment
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[lauryn]

Posted: Mon Feb 28, 2005 9:54 am Post subject:

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Finding Effective Alpha Hydroxy Acid Formulations

A basic rule of thumb to determine how active an alpha hydroxy acid product is, is to look at both the concentration of AHA and the pH of the product. An effective concentration should contain at least 8% alpha hydroxy acid with a pH between 2.5 and 4.0. A pH of up to 4.5 is acceptable on products with high concentrations of 20-25%. Products for use at home should never contain over 25% alpha hydroxy acid. For those desiring to use concentrations of over 15%, a doctor's supervision is required.

Not all alpha hydroxy acids are created equal. Some are more irritating or more moisturizing, some are better for breakouts, and some are stronger than others. Here, we will provide an outline of the main alpha hydroxy acids and a brief description of it, as well as who it is most suitable for.

Glycolic acid, the most common alpha hydroxy acid found in cosmetic preparations, is popular mainly because that is the alpha hydroxy acid that has been the most widely studied. The small molecular structure and the rapid penetration of glycolic acid make it the most irritating of the group. The possibility of irritation make glycolic acid more suitable for those with mature or non-sensitive skin. Those with oilier skin types often prefer glycolic acid sinks it sinks into the skin quickly. The widespread use of glycolic acid, though, gives the consumer flexibility on the formula. The consumer has a wide range of choices with glycolic acid products: gels, serums, lotions, creams, formulas at varying pH's and concentrations, for that contain a variety of other age-fighting ingredients. If a person wants to find a cream that contains both AHAs and vitamin C, they will have a good chance of finding a glycolic acid formulation that does.

Lactic acid is most often found in moisturizers due to its more moisturizing properties. Lactic acid is a natural humectant that draws and holds water in the upper layers of the skin. Alpha hydroxy acids as a whole can increase the skin's ability to trap water due to an increased production of natural skin moisturizers (hyaluronic acid), but lactic acid's extra humectant properties make it even more ideal for treating dry skin. Lactic acid's larger molecule size makes it less irritating than glycolic acid. Also, because lactic acid is naturally found in the human body, it is not likely to cause an allergic reaction in those with reactive skin. Lactic Acid is ideal for those with slightly sensitive, dry skin or allergy-prone skin.

Mandelic acid, an alpha hydroxy acid derived from the bitter almond, is not a widely used AHA in the cosmetic industry. It is, however, no stranger to the scientific community. Due to its natural antibacterial properties, mandelic acid is used in oral drugs to help sterilize urine and treat urinary tract infections. This alpha hydroxy acid has some unique characteristics that make it a very promising topical agent, too. With a pKa of 3.41, mandelic acid is a stronger acid than glycolic acid (3.83), yet the large molecule structure and even penetration of mandelic acid make it substantially less irritating than glycolic acid. The gentle nature of mandelic acid reduces the risk of inflammation that can sometimes occur with alpha hydroxy acid use. This quality allows those with sensitive skin, who cannot normally tolerate glycolic acid, to use AHAs - at even higher concentrations. It also makes it suitable for use on darker skin types who are at high risk for postinflammatory hyperpigmentation. The natural antibacterial properties and non-irritating nature of mandelic acid make it the ideal AHA for those trying to treat rosacea or acne.

Malic Acid, is an acid that is most commonly found in apples. Malic acid, along with tartaric acid, has unique antioxidant properties that none of the above AHAs contain. Along with its antioxidant properties, malic acid has considerable moisturizing properties. Malic acid imparts a very smooth almost slippery consistency to products. When applied to the skin, malic acid leaves a protective, moisturize coat on the skin.

Citric acid is most often used in cosmetics in a low (2-3%) concentration to adjust the pH of a product. Because we cannot find any products using solely citric acid in high enough concentrations, we do not have much information on the individual properties of this particular AHA. We will eventually conduct a few tests to check for its irritancy level and skin lightening potential.

Tartaric acid appears to be the strongest acid in the group with a pKa of 3.04 ( a difference of 1 unit of pK represents a tenfold difference in strength). It is also one of the few AHA's that has antioxidant properties. We have found a few products that contain tartaric acid, but has only been within an AHA blend.
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[lauryn]

What precautions should you take with Alpha Hydroxy Acids?

The most important precaution you can take with alpha hydroxy acids is to know the percent and pH level of the product. Always start off at alpha hydroxy acid levels of 10% or less. If you desire to step up the concentration, it is important that you do so under the supervision of a physician. Always stay at levels where irritation is minimal. Also, watch the pH level. The ideal pH is 3.0-4.0, any lower and the product may be too acidic; any higher and the product's exfoliating benefits may be nullified. Even at lower levels, though, some alpha hydroxy acids can be irritating, depending on how sensitive your skin is. Mandelic acid is the recommended AHA for those with sensitive skin, since it is the most non-irritating. Also, darker skin types should avoid glycolic acid in concentrations higher than 10%, due to the risk of hyperpigmentation. Hyperpigmentation will occur in darker skin if it becomes irritated or inflamed, so watch your skin carefully. Those with an Asian, Latin, Island, Eastern European, or Middle Eastern background should be especially careful and avoid irritating products.
More is not always better!!! Irritation and inflammation will do more damage than good. Never rush into the higher AHA concentrations. Be patient and realistic, and you should always be pleased with the results.
Remember, irritation will cause sun sensitivity, so one should always wear a sunscreen especially if one is using alpha hydroxy acids products with a low pH (2.0-3.0) or a high concentration. A minimum SPF of 15 is recommended for daily use, though an SPF of 30 is best. For more information on sunscreens, click here.
Alpha Hydroxy Acids are fruit derived and natural. A concentration under 15% should be safe for use during pregnancy.
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Can I use Alpha Hydroxy Acids with other products?

Alpha Hydroxy Acids are ideal for use with other products since they can enhance the penetration of ingredients into the skin. The one important thing to watch out for and be wary of are signs of irritation. It is always recommended to alternate the application of the AHA product and the prescription or other anti-aging cream. This is especially important with aggressive products like Retin-A, Renova, bleaching therapies, retinol, and acne topicals. It is always better to be careful with your skin and avoid overdoing it. Irritation and inflammation can contribute to the breakdown of collagen and result in damage to the skin.

[lauryn]

Ingredient Terms
Here are some ingredient terms that indicate a cosmetic contains alpha or beta hydroxy acids.

Alpha hydroxy acids:
glycolic acid
lactic acid
glycolic acid + ammonium glycolate
alpha-hydroxyethanoic acid + ammonium alpha-hydroxyethanoate
alpha-hydroxyoctanoic acid
alpha-hydroxycaprylic acid
hydroxycaprylic acid
mixed fruit acid
triple fruit acid
tri-alpha hydroxy fruit acids
sugar cane extract
alpha hydroxy and botanical complex
L-alpha hydroxy acid
glycomer in crosslinked fatty acids alpha nutrium

Beta hydroxy acids:
salicylic acid*
beta hydroxybutanoic acid
tropic acid
trethocanic acid

Alpha and beta hydroxy acids:
malic acid
citric acid

* From a chemist's perspective, salicylic acid is not a true BHA. However, cosmetic companies often refer to it as a BHA and, consequently, many consumers think of it as one.

[lauryn]

Alpha Hydrox

Alpha Hydrox Lotion and Alpha Hydrox Face Creme were two of the more effective and reasonably priced alpha hydroxy acid products that first appeared on the market when the AHA craze was launched back in 1992. While other companies often hedge when telling you how much AHA their products contain, Alpha Hydrox is one of the few companies that is more than forthcoming about their contents. The AHA in these products is glycolic acid, which is considered one of the best (aside from lactic acid), and the pH of the products is at a level that makes AHAs effective.

Extra Strength AHA Oil-Free Formula, 10% AHA Facial Treatment ($9.29 for 1.7 ounces) is virtually free of any ingredients that could clog pores and is a very good option for an AHA exfoliant for someone with normal to oily skin. This does contain a good anti-irritant. www.drugstore.com/products/prod.asp?pid=16742&catid=21503&trx=PLST-0-SRCH&trxp1=21503&trxp2=16742&trxp3=1&trxp4=0&btrx=BUY-PLST-0-SRCH

Fade Cream ($8.29 for 3.5 ounces) could have been a very good 2% hydroquinone-based skin lightener in a fairly standard moisturizer base for normal to dry skin, but the packaging (in a jar) means the hydroquinone will be unstable after opening because of exposure to air.
www.drugstore.com/products/prod.asp?pid=45945&catid=21503&trx=PLST-0-SRCH&trxp1=21503&trxp2=45945&trxp3=1&trxp4=0&btrx=BUY-PLST-0-SRCH


PRODUCT RATING KEY:
identifies a "Paula's Pick," meaning a product that exceeds expectations and goes beyond the criteria for a product in its category with minimal to no concerns. Note: Hair-care products never receive a Paula’s Pick rating because there are so many excellent products with remarkably similar formulations, none stand out as truly “superior.”<br>_________________

[lauryn]

Useful in treating dry skin, acne, liver or sun spots, lessening fine facial wrinkles, and improving skin texture, alpha hydroxy acids also increase skin thickness and encourage collagen production. Glycolic acid is the most popular of the alpha hydroxy group. Glycolic acid appears to be the most effective AHA for use in skin rejuvenation because it has a small molecule which allows it to penetrate the skin easily. Glycolic acid helps dissolve the “glue” that holds the keratinized skin cells together and increases cell exfoliation and replacement. Skin becomes smoother and more even in tone. As well, glycolic acid reduces surface oils, a benefit for battling blemishes. Glycolic acid and other alpha hydroxy formulations can be irritating, as mentioned above.

[lauryn]

Alpha-Hydroxy Acids
by Dr. Dennis T Sepp, As published in Les Nouvelles Esthetiques,
Dr. Dennis T. Sepp is a PhD chemist with a degree from the University of California at Santa Barbara. He has taught Chemistry at the University level and has conducted research in medicinal chemistry. He is the owner and formulator for ShiKai Products and continues to lecture and write about natural cosmetic formulations. Do you have a question about cosmetic formulations? e-mail him at: [e-mail]

General Background

AppleLong before the chemical structure, or even the existence, of alpha-hydroxy acids (AHA's) were known, they were unknowingly being used as an ingredient for improving the condition of skin. Egyptian women took baths in sour milk in order to improve their skin. French women in the court of Louis XIV washed their faces with old wine for the same reasons. Old fashioned facial masks made from fruit, honey or yogurt were also unknowingly taking advantage of AHAs as their active ingredients.

Alpha-hydroxy acids are commonly found and isolated from fruits of allOrange sorts. That is why they are referred to as fruit acids. For example, malic acid is found in apples, citric acid can be isolated from most all citrus fruits and glycolic acid is commonly found in honey or sugar cane. Another source of AHAs is from the fermentation of natural products. Lactic acid is found in milk that has soured, and tartaric acid can be isolated from fermented grapes (wine). It is this natural, feel good origin of alpha-hydroxy acids that make them so appealing. Couple this with the genuine hi-tech biochemistry that they exhibit and it is no mystery as to why they are so popular today.

A Little Chemistry: Organic vs. Mineral Acids

Chemically speaking, an alpha-hydroxy acid is a low molecular weight organic acid. Most people associate the word "acid" with potent and dangerous acids like hydrochloric and sulfuric. These acids are called mineral acids and are indeed potent and dangerous. Most are strong enough to dissolve metals. An organic acid however, differs greatly from a mineral acid. Organic acids are much, much milder than mineral acids and occur quite commonly in everyday life. Acetic acid, for example, is the organic acid that gives vinegar its characteristic sour taste.

An organic acid is chemically defined as a molecule that possesses a carboxylic acid (-COOH) group:

Acetic Acid (CH3-COOH); Glycolic Acid (CH2OH-COOH) Lactic Acid (CH3-CHOH-COOH) Beta Hydroxy Acid (CH2OH-CH2-COOH)

An AHA such as glycolic or lactic acid has a hydroxyl group (-OH) present on the carbon atom immediately adjacent to the acid group. This position is defined as "alpha" (first letter of the Greek alphabet) because it is the first carbon next to the acid group. Beta-hydroxy acids are thus molecules where the hydroxy group is on the second carbon next to the acid group. Glycolic Acid is the most commonly used AHA. Because of its small molecular weight and size, it is presumed to have a better capacity to penetrate skin. Lactic acid on the other hand, has a larger molecular weight than glycolic acid but is capable of being converted in vivo to pyruvic acid (an alpha keto acid) which is presumed to be a more effective exfoliating agent. It should be noted that neither salicylic acid nor retinoic acid are alpha-hydroxy acids.

Current Uses

Today, alpha-hydroxy acids are used extensively in cosmetic dermatology (1). At concentrations lower than 10%, they are regularly formulated into everyday use creams. At these levels, skin benefits result from continuous use and result in a gradual reduction in fine lines and an overall improvement in skin texture brought about by accelerated desquamation (exfoliation). At higher concentrations, AHAs function as peeling agents which act more rapidly and at a deeper level (7). Glycolic acid peels at concentrations of 20-70% are commonly used by dermatologists and plastic surgeons to remove severe acne scarring and skin pigmentation irregularities. Their effectiveness depends on the contact time of the acid and the number of peeling sessions (2). Milder peels (10-40%) can be carried out in skin care salons. Peels, in general, are being used more frequently to treat the wrinkles and skin discoloration resulting from solar damaged skin (actinic aging). They are also finding more and more use as anti-aging ingredients to combat the loss of smoothness and skin elasticity associated with chronological aging. The war against wrinkles seems to be never ending.

How AHAs Work

The full mechanism of action of alpha-hydroxy acids is not yet fully understood (3). It is known however, that they function in two distinct fashions: First, they can act as a simple humectant that absorbs moisture from the atmosphere. When applied to the skin, these hydrated AHAs act to increase the water content of the skin and thus moisturize the outer layer of the epidermis (the stratum corneum) and consequently make the skin softer and more flexible. The second method by which AHAs are thought to act is by reducing corneocyte adhesion and accelerating cell proliferation within the deeper basal layer of the skin (4,5,6). This exfoliating action of AHAs occurs as a result of their ability to break the bonds between dead skin cells that form at the surface of the skin. Skin normally has a dead layer of cells at its surface (the corneocyte layer), and AHAs can speed up the normal process of skin cell regeneration and sloughing. This results in increased flexibility of the skin as well as decreased formation of large dry skin flakes at the surface of the skin. When applied in the high concentrations of a peel, AHA's operate at a deeper level and cause detachment of keratinocytes and epidermolysis. At lower concentrations, AHAs primarily reduce intercorneocyte cohesion thus promoting exfoliation and thinning of the stratum corneum. A thinner stratum corneum is more compact and flexible (8).

Sun damaged skin is becoming more and more of a problem in our society. Prematurely aged skin brought about by long term UV radiation exposure (actinic aging), is in part caused by a thickening of the stratum corneum resulting from increased corneocyte cohesion (9). Long term UV radiation exposure also degrades collagen in the dermis layer of the skin. There is also evidence that excessive amounts of abnormal elastic fibers also tend to accumulate within the dermis of photodamaged skin (10). Glycolic acid at low concentrations works well to decrease corneocyte cohesion by promoting exfoliation of the outer layers of the stratum corneum (11,12). This is especially relevant since most pigmentation alterations associated with photodamage can be attributed to the thickening of the stratum corneum (10).

Most of the evidence on how AHAs work seems to point to exfoliation and the resulting turnover of new cells in the outer epidermal layer of the skin. There is increasing evidence however, that AHAs may be working at a much deeper level. There may well be increases in procollagen and Type I collagen that occur in the deeper dermis layer brought about by long term treatment with AHAs (13). One interesting study showed that topical treatment twice a day for 3 months with a 5% glycolic acid cream, at pH 2.8, affected surface and epidermal changes, while the same treatment, but with a 12% cream, reached deeper and influenced both the epidermis and the deeper dermis layer, and resulted in increased epidermal and dermal firmness and thickness. Both showed clinical improvement in skin smoothness and in the appearance of lines and wrinkles (15). Another interesting study showed that AHAs may thin the outer stratum corneum, but actually end up increasing the overall thickness of the epidermis. This thickening is accompanied by increased synthesis of glycosaminoglycans and collagen (14). It is becoming apparent that alpha-hydroxy acids may do more than just increase exfoliation and skin cell turnover.

[lauryn]

Requirements for Effectiveness

The efficacy of an alpha-hydroxy acid when used as an exfoliating agent depends upon the concentration of the AHA and the pH of the medium in which it is used. But surprisingly, it does not depend upon the specific AHA that is used. For example, glycolic acid and lactic acid applied at equal concentrations and at the same pH have just about the same cell renewal rates (16). Furthermore, this same study showed that just about all of the small organic acids tested had similar cell renewal rates. It did not seem to matter whether you were testing alpha-hydroxy acids, beta-hydroxy acids or even the non-hydroxy acids like acetic or pyruvic acid. Only trichloroacetic acid was measurably more potent. All acids tested however, showed an increase in cell renewal stimulation with increased concentration. And all acids tested showed a marked decrease in cell renewal with increasing pH. The optimum pH for cell renewal stimulation was at about 3.0. At a pH above 6.0 very little stimulation was observed for any of the acids. In general, AHAs at a pH of 6.0 or greater behave more like moisturizers than exfoliating agents. There is, of course, no optimum concentration for the use of an AHA. It depends upon how it is being used, whether by a physician using it as a peel (up to 70%), or by a consumer using an over-the-counter cream (about 10%). Safety is the primary consideration for determining at what concentration an AHA should be used.

The relationship between the strength of an AHA and the pH at which it is being used cannot be overestimated. Intuitively one can recognize that a higher concentration of AHA should be more potent. But the effect of pH on potency is more subtle. It must be recognized that it is the free acid form of the AHA molecule that is responsible for cell renewal stimulation. It is generally accepted that 4% free acid is usually the threshold minimum for this effect (17). It can be mathematically calculated that in order to have 4% free acid available at a pH of 3.8 one needs to start with 8% alpha-hydroxy acid. If the pH of the same preparation were lowered to approximately 1.0, the available free acid would increase to greater than 7%. And conversely, if the pH were increased to 6.0 or greater, the available free acid would drop well below 1%. Thus it can be seen that the same 8% AHA formula could work as a truly potent (but very irritating) skin cell renewal stimulator if the pH were 1.0. Or, it could end up as just a mild moisturizer if formulated at pH 6.0 or higher. It is for this reason that an alpha-hydroxy acid preparation sold to the public should be labeled with not only the identity of the AHA used, but also with its concentration and the pH of the preparation.

Long Term Effects and Safety Concerns

Although alpha-hydroxy acids appear to be the miracle cosmetic ingredients of the 90s, there are genuine safety concerns associated with their extended use. The FDA is directly concerned with two primary issues: sun sensitivity and the long term effects brought about from the usage of a skin irritant.

Does the use of AHAs make the user more sensitive to sunlight and consequently more at risk for photodamage and photocarcinogenity? The Cosmetic & Ingredient Review (DRI), an independent panel formed by the CTFA (Cosmetic, Toiletry and Fragrance Association), conducted a study on the safety of glycolic acid and lactic acid. They concluded that on a professional level (skin salons) these AHAs could safely be used at a concentration 30% or less and at a pH of 3.0 or greater. The CTFA study also recommended that retail products contain 10% or less AHA and maintain a pH of 3.0 or greater. In both cases they recommended that the person treated with AHA's should use sun protection of at least SPF 15 (18). Although this study did not find that AHAs promoted sun sensitivity, they did find that people with light hair and fair skin do experience increased sunburn-cell levels when exposed to sunlight using a 10% solution of AHA. It was felt however, that this result was not significant since people with this kind of skin are predisposed to sun damage.

The effects of long term usage of alpha-hydroxy acids is just now being addressed. Any answers will have to wait until someone determines how alpha-hydroxy acids actually work. As yet there are no definitive studies from either industry or academia and the FDA has started a study on their own. The fact that the FDA is genuinely interested is evident from this statement by Dr. John Bailey, director of the FDA's Office of Cosmetics & Colors: "The fact that these are chemical irritants that are being sold and directed to be used over a long time raises the issue of chronic irritation and potential adverse effects."

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