Azelaic Acid Nonanedioic Acid: Naturally Occurring Dicarboxylic Acid with Multitarget Activity Against Acne, Rosacea and Pigmentation Disorders

Overview and Applications of Azelaic Acid

I. Chemical Nature and Sources

• Chemical Nature: Azelaic acid is a saturated straight-chain dicarboxylic acid containing 9 carbon atoms, with the chemical formula C₉H₁₆O₄ and a molecular weight of 188.22.
• 
  
• Sources:
  • Natural Occurrence: Widely found in grains such as rye, barley, and wheat, and can also be produced by Malassezia species on the human skin surface.
  • Industrial Synthesis: Derived from oleic acid through processes such as ozonolysis or peroxide oxidation.

II. Physiological Properties

1. Antimicrobial Activity:
   • Inhibits various bacteria, including Propionibacterium acnes and Staphylococcus epidermidis, with no reported resistance.
   • Exhibits antifungal effects against organisms like Candida albicans.
   • 
     
2. Anti-inflammatory Effects:
   • Blocks inflammatory signaling pathways, reducing the release of pro-inflammatory cytokines (e.g., IL-6, TNF-α).
   • Suitable for inflammatory skin conditions such as rosacea and seborrheic dermatitis.
   • 
     
3. Keratolytic Regulation:
   • Reduces filaggrin synthesis to prevent excessive follicular keratinization.
   • Improves issues like enlarged pores and comedones.
   • 
     
4. Skin Lightening and Spot Fading:
   • Inhibits tyrosinase activity, reducing melanin synthesis.
   • Interferes with melanosome transfer, lowering epidermal melanin content.
   • 
     
5. Sebum Control:
   • Competitively inhibits 5α-reductase to reduce sebum production.
   • Beneficial for oily skin and acne-prone individuals.
6. 
   
7. Safety:
   • Low systemic absorption with topical application; minimal systemic toxicity.
   • Considered safe for use during pregnancy and lactation (Category B).

III. Clinical Applications

1. Acne Treatment:
   • Mechanism: Antimicrobial, anti-inflammatory, and keratolytic effects.
   • 
     
   • Guidelines: Recommended as a second-line topical agent for mild to moderate acne (Chinese Acne Treatment Guidelines, 2019 revision). Approved by the FDA at 20% concentration.
   • 
     
2. Melasma Management:
   • Mechanism: Inhibits melanocyte activity and reduces pigmentation.
   • Guidelines: Recommended at 15–20% concentration for 6 months (Chinese Expert Consensus on Melasma Diagnosis and Treatment, 2021).
   • 
     
3. Rosacea:
   • Effect: Reduces erythema and papulopustules via anti-inflammatory action.
   • Approved Formulation: 15% gel (PDA-approved).
   • 
     
4. Other Uses:
   • Post-inflammatory hyperpigmentation (e.g., acne marks), seborrheic dermatitis, and superficial fungal infections.

IV. Usage Precautions

1. Irritation Potential:
   • May cause transient, mild skin irritation (e.g., stinging, burning), which typically resolves with continued use.
   • Patch testing is recommended before initial application.
   • 
     
2. Application Guidelines:
   • Concentration: Commonly available at 10%, 15%, or 20%.
   • Frequency: Once or twice daily, adjusted based on skin tolerance.
   • Combination Therapy: Can be paired with retinoids or vitamin C for enhanced anti-aging effects.
   • 
     
3. Important Notes:
   • Avoid contact with eyes and the perioral area.
   • Follow up with moisturization and sunscreen to prevent dryness and hyperpigmentation.