Alpha hydroxy acids (AHAs) are a group of natural acids derived from plants and animals, commonly found in cosmetic and skin care products. Valued for their exfoliating effects, they are used to improve complexion, treat acne, and promote skin cell turnover. This article explores the benefits and risks associated with using AHAs on the face, providing a comprehensive overview for informed decision-making.
What are Alpha Hydroxy Acids?
Alpha hydroxy acids (AHAs) are organic acids with a hydroxyl group attached to the alpha position of the acid. These acids are derived from various natural sources, including:
- Glycolic acid: From sugar cane, known for its ability to penetrate the outer layers of skin.
- Lactic acid: Found in sour milk and fermented vegetables, considered gentler on the skin.
- Citric acid: Derived from citrus fruits, functioning as a pH adjuster and humectant.
- Malic acid: Present in apples and other fruits.
- Tartaric acid: Found in grapes.
AHAs are one of three types of exfoliating acids, the others being beta hydroxy acids (BHAs) and polyhydroxy acids (PHAs). Within the AHA category, glycolic, lactic, malic, tartaric, and citric acids are commonly used in skin care products. Glycolic acid is frequently used in anti-aging products due to its ability to penetrate the outer layers of skin.
Benefits of Alpha Hydroxy Acids
- Exfoliation: AHAs remove the outer layer of dead skin cells, resulting in smoother, more even-toned skin. The exfoliating effects depend on the concentration of AHAs in the product. AHAs diminish corneocyte cohesion immediately above the granular layer by detaching and desquamating the stratum corneum.
- Promotion of New Skin Cells: By exfoliating the skin and removing old skin cells and collagen fibers, AHAs stimulate the production of new protein-rich fibers, enhancing skin appearance. AHAs can improve wrinkled skin by increasing the synthesis of glycosaminoglycans and thickening skin.
- Acne Improvement: AHAs remove built-up dirt and debris that can clog pores, helping to improve or prevent acne.
- Reduction of Fine Lines and Wrinkles: AHAs increase skin thickness and smooth out fine lines and wrinkles. Research published in the Journal of the American Academy of Dermatology shows that a lotion containing 25 percent glycolic, lactic, and citric acid improved skin thickness, elastic fiber quality, and collagen density.
- Improved Complexion: AHAs increase blood flow, which can improve skin complexion.
- Reduction of Sun Spots: AHAs are used to reduce sun spots caused by UV light exposure.
- Treatment of Skin Conditions: AHAs are used topically to treat extremely dry skin (xerosis), inherited dry, scaly skin (ichthyosis), and skin darkening (melasma).
- Brightening Complexion: AHAs with glycolic acid can break down skin cell accumulation, while products with citric acid can brighten skin even further. AHAs have anti-inflammatory properties that can help promote blood flow to the skin, which can help correct pale, dull complexions. Proper blood flow also ensures that skin cells get the necessary nutrients needed via oxygen-rich red blood cells.
- Increased Product Absorption: AHAs can make existing products work better by increasing their absorption into the skin. AHAs like glycolic acid can break through the layer of dead skin cells, enabling moisturizers to hydrate new skin cells more effectively.
Potential Risks and Side Effects
- Skin Irritation: AHAs can cause mild skin irritation, redness, swelling, itching, and skin discoloration. Facial peels, lotions, and creams with concentrations greater than 10% should be used under the supervision of a dermatologist.
- Increased Sun Sensitivity: AHAs can make the skin more sensitive to sunlight. The FDA recommends using products with an AHA concentration of 10% or less and a pH of 3.5 or above, along with SPF protection.
- Adverse Reactions: Caution should be exercised due to potential adverse reactions, including redness, swelling, burning, and pruritus. The Food and Drug Administration (FDA) does not raise serious safety concerns regarding GA used topically at low concentrations.
- Over-Exfoliation: Overuse of AHA products can damage the skin barrier, leading to irritation, burning, dryness, flakiness, blotchiness, and increased sensitivity.
- Hyperpigmentation in Darker Skin: In darker skin tones, AHAs can cause dark spots and changes in skin tone.
How to Use Alpha Hydroxy Acids Safely
- Start Slowly: If new to AHA products, begin by using them every other day.
- Concentration: Use products with an AHA concentration of 10% or less for over-the-counter use. Products with higher concentrations should be used under a dermatologist's supervision.
- Sun Protection: Protect skin from sunlight by using sunscreen daily. The FDA recommends using products with SPF protection. The AAD recommends using a daily sunscreen that is broad-spectrum, water resistant, and SPF 30 or higher.
- Patch Test: Test the product on a small area of skin before applying it to a larger area.
- Avoid Broken Skin: Do not use AHAs on broken skin or sunburned skin.
- Follow Directions: Carefully follow the directions on the product label.
- Consult a Dermatologist: If unsure of which product to choose or if signs of overuse appear, consult a dermatologist.
- Pregnancy and Breastfeeding: Alpha hydroxy creams at a concentration of 10% or less are likely safe when applied to the skin during pregnancy and breast-feeding.
Wash-off AHAs
To use a wash-off AHA, such as a cleanser, follow the instructions on the label. The AAD recommends:
- Applying the product using small, circular motions
- Leaving for 30 seconds
- Rinsing with lukewarm water
- Following with moisturizer
Leave-on AHAs
For leave-on products, follow the instructions on the label. Some people prefer to apply leave-on products before sleep so that the products can work overnight.
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AHA Peels
AHA peels are prescription-strength treatments that can treat more pronounced skin concerns, such as rough texture or hyperpigmentation. A dermatologist can carry out AHA peels in their office. They take around 15-20 minutes. First, a dermatologist will cleanse the skin, then apply the solution, which can range from 20-70% in strength. The solution sits on the skin for several minutes before a person washes it off. People can use glycolic acid peels once every 1-2 weeks.
Regulatory Compliance and Safety Standards
- FDA Guidelines: The US FDA issued guidance on AHA concentrations in 2005, recommending that cosmetic products contain no more than 10% AHA, with a pH of 3.5 or higher for over-the-counter use. It should either be formulated with an SPF, or its labels contain a clear statement to use an appropriate SPF.
- EU Standards: The European Union (EU) adheres to more stringent regulatory standards. The EU’s Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers (SCCS) recommended that glycolic acid be used safely at concentrations up to 4% with a pH of at least 3.8, and lactic acid up to 2.5% with a pH of at least 5.
- Australian Regulations: Australia’s National Industrial Chemicals Notification and Assessment Scheme (NICNAS) considered that the chemical is corrosive at concentrations less than 30% and only slightly irritants at 10%, and thus they suggested establishing a level of irritant and corrosive effect between 10-25%.
AHAs vs. BHAs
Alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) are both acids used in cosmetics, but they differ in their source and properties. BHAs are often used for acne treatment and improving sun damage. Salicylic acid is the most common BHA in skin care products. BHAs are found to be more effective for oily and acne-prone skin because they can improve skin texture, reduce the shedding of skin cells inside pores, and break down blackheads and whiteheads.
Market Trends
The global market for alpha-hydroxy acids (AHAs) is undergoing significant expansion, propelled by increasing demand for skincare products that address aging and environmental damage. In 2021, the total value of the global AHAs market was estimated at $1.2 billion. The use of AHAs in cosmetic formulations is a growing market, with many skincare brands offering products containing different AHAs and formulations.
Research and Studies
- UV Sensitivity Studies: Studies have confirmed that applying AHAs to the skin increases UV sensitivity. After four weeks of AHA application, volunteers' sensitivity to skin reddening produced by UV increased by 18 percent.
- Photocarcinogenesis Study: A study determined that glycolic acid did not affect photocarcinogenesis in mice, and that salicyclic acid had a photoprotective effect in mice.
- Collagen and Procollagen Production: Citric acid was observed to stimulate the production of collagen I and procollagen II, whereas glycolic acid enhanced the epidermis and dermis, proving the efficacy of AHAs in reversing photoaged skin.
- Apoptosis Induction: Citric acid (12.5 mM) was discovered to trigger apoptosis through the caspase-dependent pathway by activating caspase-9 and caspase-3.
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