AHA vs BHA: Key Differences & When to Use Each Acid for Effective Skincare
Customize your exfoliation to target skin concerns for smoother, brighter skin.
Chemical exfoliation is a cornerstone of modern skincare, with alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) becoming go-to ingredients for clearer, smoother, and more radiant skin. Despite their similar functions as exfoliants, AHAs and BHAs differ in their structure, mode of action, skin benefits, and recommended use. This comprehensive guide explores the science, advantages, and best practices for incorporating these powerful acids into your routine.
Table of Contents
- What Are AHA and BHA?
- How Do AHA and BHA Work?
- Common Types of AHAs and BHAs
- Key Differences Between AHAs and BHAs
- Benefits of AHA and BHA
- Side Effects and Risks
- How to Choose: Which Acid Is Right for Your Skin?
- Application Tips and Best Practices
- Can You Use AHA and BHA Together?
- Frequently Asked Questions
- AHA vs BHA: At-a-Glance Comparison
What Are AHA and BHA?
Alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) are chemical exfoliants found in numerous skincare products such as cleansers, toners, serums, and peels. Both types of acids belong to the broader group of hydroxy acids, derived from natural and synthetic sources, and are celebrated for their ability to remove dead skin cells and boost cell turnover.
- AHAs: Water-soluble acids typically sourced from fruits, milk, or plants. Common AHAs include glycolic acid and lactic acid.
- BHAs: Oil-soluble acids, with salicylic acid being the most well-known and widely used.
While both exfoliate, they differ in how and where they work on the skin.
How Do AHA and BHA Work?
Exfoliation is the key function of both acids, but via distinct mechanisms:
- AHAs: Gently break the bonds holding dead skin cells to the skin’s surface, revealing fresher skin underneath; they act on the outermost layer (epidermis).
- BHAs: Penetrate deeply into pores due to their oil-solubility, dissolving excess sebum and clearing out clogged debris within follicles.
This difference explains why each acid type is preferable for different skin concerns and types. AHAs provide broad surface benefits suited to dry or sun-damaged skin, while BHAs are ideal for oily, congested, or acne-prone complexions.
Common Types of AHAs and BHAs
Alpha Hydroxy Acids (AHAs)
- Glycolic Acid: Derived from sugar cane; the smallest molecule, highly effective for exfoliation and anti-aging.
- Lactic Acid: Derived from milk; gentler, with extra hydrating properties.
- Citric Acid: Sourced from citrus fruits; sometimes classified as both an AHA and BHA due to its properties.
- Malic, Tartaric, and Mandelic Acid: Derived from fruits and nuts; typically used in combination for additional exfoliating effects or sensitivity concerns.
Beta Hydroxy Acids (BHAs)
- Salicylic Acid: The primary and most effective BHA, renowned for acne treatment due to its pore-clearing and anti-inflammatory abilities.
Polyhydroxy acids (PHAs) are a newer, even gentler AHA-related group (including lactobionic acid and gluconolactone), suitable for extremely sensitive or mature skin.
Key Differences Between AHAs and BHAs
The following table summarizes how these two families of acids differ:
| Aspect | AHA (Alpha Hydroxy Acid) | BHA (Beta Hydroxy Acid) |
|---|---|---|
| Solubility | Water-soluble | Oil-soluble |
| Where They Work | Surface of the skin | Inside pores as well as surface |
| Main Benefits | Improves texture, tone, pigmentation, wrinkles | Unclogs pores, reduces acne, controls oil |
| Best For | Dry, sun-damaged, normal skin | Oily, acne-prone, combination skin |
| Sun Sensitivity | Increases sun sensitivity (use SPF) | Lower risk, but SPF still recommended |
| Other Effects | Boosts collagen | Anti-inflammatory, antibacterial |
Benefits of AHA and BHA
Benefits of AHAs
- Smooths skin texture by accelerating removal of dead cells
- Reduces signs of aging such as fine lines and wrinkles by promoting collagen
- Fades hyperpigmentation including sun spots, melasma, and acne scars
- Improves moisture levels in the skin when using lactic acid
- Enhances overall brightness, revealing a radiant complexion
Benefits of BHAs
- Unclogs pores and prevents breakouts by dissolving oil and debris inside follicles
- Reduces blackheads and whiteheads, the most stubborn types of acne congestion
- Calms inflammation and redness thanks to anti-inflammatory properties
- Controls excess oil, making it very suitable for oily or combination skin types
- Helps with sun damage to some extent by improving skin texture
Side Effects and Risks
Both AHA and BHA are considered safe when used as directed, but each has potential drawbacks:
- AHAs: Can cause irritation, stinging, redness, and serious increased sun sensitivity; always use daily SPF.
- BHAs: May cause dryness or irritation at higher concentrations, but generally have skin-calming properties and less risk of photosensitivity.
Overuse of either can disrupt the skin barrier. Start with lower concentrations and increase frequency slowly.
How to Choose: Which Acid Is Right for Your Skin?
The best acid for you depends on your skin type and key concerns:
- Dry, dull, or sun-damaged skin: AHAs help restore radiance and smooth texture.
- Sensitive skin: Lactic acid (a milder AHA), PHAs, or lower-dose BHAs may be better tolerated.
- Oily, congested, or acne-prone skin: BHAs (mainly salicylic acid) are most effective for clearing clogged pores and reducing blackheads.
- Mature skin with hyperpigmentation or wrinkles: AHAs—especially glycolic acid—help brighten, even tone, and smooth fine lines.
- Combination skin: Balanced approach, with preference for BHA in oilier zones and AHA elsewhere.
Consult with a dermatologist before starting any new exfoliant if you have a history of eczema, rosacea, or very sensitive/reactive skin.
Application Tips and Best Practices
- Patch Test: Always test a new acid product on a small area for 24 hours before first use.
- Start Slow: Begin two or three times a week, then gradually increase frequency as tolerated.
- Apply to Clean, Dry Skin: For most leave-on exfoliants, this enhances absorption and even activity.
- Use Moisturizer: Hydrate and protect your barrier, especially if dryness occurs.
- Never Skip Sunscreen: AHAs in particular make your skin much more prone to sunburn and damage.
Can You Use AHA and BHA Together?
Some products and protocols combine both acids for amplified exfoliation and improved results—especially for combination skin types. However, layering multiple strong acids can increase the risk of irritation, dryness, and sensitivity. If combining, either use them on alternate days or opt for professionally formulated mixes where concentrations are balanced.
Expert tip: If using high-strength peels or treatments, avoid layering multiple acid types at home, especially if new to chemical exfoliation. Always listen to your skin’s response and err on the side of caution.
Frequently Asked Questions (FAQs)
Q: Can people with sensitive skin use acids?
Individuals with sensitive skin should opt for milder acids like lactic acid (AHA) or polyhydroxy acids (PHAs). Always start at low concentrations and test first. BHAs generally have skin-calming properties, but overuse can trigger dryness.
Q: How do I know if I’m over-exfoliating?
Signs of over-exfoliation include redness, flaking, increased sensitivity, and burning sensations. If you notice these, stop acids temporarily, focus on gentle hydration, and reintroduce only after your barrier repairs.
Q: Should acids be used in the morning or night?
Acids can be used at either time, but many prefer nighttime use to minimize sun exposure during peak sensitivity. If using an AHA during the day, SPF is essential.
Q: What concentration of AHA/BHA should beginners use?
For AHAs, start with 5% or less glycolic/lactic acid; for BHAs, 0.5–2% salicylic acid is the general safe range for most skin types.
Q: Can pregnant or breastfeeding women use AHA/BHA?
Generally, lactic acid (AHA) is considered low risk in pregnancy but consult your healthcare provider. High doses of salicylic acid should be avoided in pregnancy.
AHA vs BHA: At-a-Glance Comparison
| Feature | AHA | BHA |
|---|---|---|
| Main Acid Types | Glycolic, Lactic, Mandelic | Salicylic acid |
| Solubility | Water | Oil |
| Best For | Dry, dull, aging, uneven skin tone | Oily, acne-prone, congested |
| Benefits | Texture, pigmentation, hydration, anti-aging | Pore-clearing, anti-acne, anti-inflammatory |
| Risks | Sun sensitivity, irritation | Dryness (at high strengths) |
| Notable Products | Toners, peels, creams | Cleansers, serums, spot treatments |
| Frequency | 2–7x/week (product-dependent) | Daily–3x/week (product-dependent) |
References
- eightsaintsskincare.com/blogs/page-eight/ahas-and-bhas-what-s-the-difference-and-how-do-they-work
- healthline.com/health/aha-vs-bha
- dermstore.com/blog/aha-vs-bha
- medicalnewstoday.com/articles/aha-vs-bha
- eternaldermatology.com/what-is-the-difference-between-alpha-and-beta-hydroxy-acids-in-skincare
- columbiaskinclinic.com/skin-care/ahas-vs-bhas
- thenakedchemist.com/understanding-beta-and-alpha-hydroxy-acid
References
- https://eightsaintsskincare.com/blogs/page-eight/ahas-and-bhas-what-s-the-difference-and-how-do-they-work
- https://www.healthline.com/health/aha-vs-bha
- https://www.dermstore.com/blog/aha-vs-bha/
- https://www.medicalnewstoday.com/articles/aha-vs-bha
- https://www.eternaldermatology.com/what-is-the-difference-between-alpha-and-beta-hydroxy-acids-in-skincare/
- https://columbiaskinclinic.com/skin-care/ahas-vs-bhas/
- https://thenakedchemist.com/understanding-beta-and-alpha-hydroxy-acid/
- https://moonjuice.com/blogs/ingredients/whats-the-difference-between-aha-bha
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