What are the differences between Alpha Hydroxy Acid (AHA) peels, Beta Hydroxy Acid (BHA) peels, and Lipohydroxy Acid (LHA) peels in terms of treatment and benefits?

Chemical Peels: AHA vs BHA vs LHA

Direct Comparison and Selection

For acne treatment, both AHA (glycolic acid) and BHA (salicylic acid) peels demonstrate equivalent efficacy, but salicylic acid offers sustained effectiveness with fewer adverse events, making it the preferred choice for most acne patients. 1

Alpha Hydroxy Acids (AHA) - Glycolic Acid Peels

Mechanism and Characteristics

• AHAs are water-soluble organic acids that induce controlled exfoliation of old skin and stimulate new epidermal growth with more evenly distributed melanin 2
• Glycolic acid penetrates to the dermal layer, triggering wound-healing activities that cause skin remodeling and smoothing 2
• The depth of penetration depends on concentration (30-70%), number of coats applied, and contact time 3, 4

Clinical Applications

• Primary indications include: acne, acne scars, melasma, postinflammatory hyperpigmentation, photoaging, and seborrhea 4
• For postacne pigmentation specifically, glycolic acid 50% demonstrates superior efficacy compared to salicylic acid 30%, with 45% of patients achieving >75% reduction in pigmentation versus 0% with salicylic acid 5
• The American Academy of Dermatology recognizes glycolic acid as an effective topical agent for acne vulgaris 6

Concentration Guidelines

• Very superficial peels: 30-50% glycolic acid applied for 1-2 minutes 3
• Superficial peels: 50-70% glycolic acid applied for 2-5 minutes 3
• Medium-depth peels: 70% glycolic acid applied for 3-15 minutes 3
• Treatment protocols typically involve application every 15 days for 4-6 months 3

Safety Profile and Adverse Events

• More adverse events occur with glycolic acid compared to salicylic acid, particularly after initial treatment 1
• Common side effects include swelling, burning, and pruritus 7
• Absolute contraindications: isotretinoin therapy within 6 months, active infection/open wounds, psychological instability, and poor general health 3
• Relative contraindications: abnormal scar formation history, recent radiation, active rosacea, recent resurfacing procedures within 3-12 months 3
• Safe for Fitzpatrick skin types I-IV 4

Beta Hydroxy Acids (BHA) - Salicylic Acid Peels

Mechanism and Characteristics

• BHAs are lipid-soluble, allowing deeper penetration into sebaceous follicles compared to water-soluble AHAs 1
• This lipophilic property makes salicylic acid particularly effective for oily, acne-prone skin 1
• The American Academy of Dermatology recognizes salicylic acid as an effective topical agent and chemical peel option for acne vulgaris 6

Clinical Applications

• Primary indication: mild to moderately severe facial acne vulgaris 1
• Demonstrates sustained effectiveness at 2 months post-treatment, unlike glycolic acid 1
• Both 30% salicylic acid and 30% glycolic acid show significant effectiveness by the second treatment with no significant difference in initial efficacy 1

Treatment Protocol

• Standard concentration: 30% salicylic acid 1, 5
• Applied every 2 weeks for total of six treatments 1
• Can be used as part of field treatment for actinic keratosis 6

Safety Profile

• Fewer side effects compared to glycolic acid peels, particularly after initial treatment 1
• Better tolerated overall with sustained long-term effectiveness 1

Lipohydroxy Acid (LHA) Peels

Current Evidence Status

No guideline-level evidence exists for LHA peels in the provided literature. The major dermatology guidelines from the American Academy of Dermatology and British Association of Dermatologists do not address LHA as a distinct chemical peel category 6. LHA is a derivative of salicylic acid but lacks the robust clinical trial data and guideline recommendations that support AHA and BHA use.

Clinical Decision Algorithm

For Acne Treatment:

1. First-line choice: 30% salicylic acid peel (BHA) - sustained effectiveness with fewer adverse events 1
2. Alternative: 30-50% glycolic acid peel (AHA) - equivalent initial efficacy but more side effects 1
3. Apply every 2 weeks for 6 treatments 1

For Postacne Pigmentation:

1. Preferred choice: 50% glycolic acid peel (AHA) - superior pigmentation reduction 5
2. Apply every 2 weeks for up to 6 weeks 5

For Photoaging and Melasma:

1. Glycolic acid peels (AHA) at 30-70% concentration depending on desired depth 3, 4
2. Requires pre-peel priming and careful patient selection 4

Critical Pitfalls to Avoid

• Never use glycolic acid peels on the face without proper concentration control - risk of irritant burning 6
• Do not perform peels within 6 months of isotretinoin therapy - absolute contraindication 3
• Avoid in patients with active infections, open wounds, or poor wound healing 3
• Do not confuse clinical peel concentrations (30-70%) with home-use formulations (7-15%) - these serve entirely different purposes 3
• Always use broad-spectrum sunscreen after AHA peels due to photosensitivity risk 7
• Proper timing of neutralization is essential to prevent excessive depth and complications 4