What is the best treatment for chronic acne with hyperpigmentation on the back and underarms?

Treatment for Chronic Acne with Hyperpigmentation on Back and Underarms

Start immediately with a topical retinoid (adapalene 0.1% gel available over-the-counter or prescription tretinoin/tazarotene) combined with benzoyl peroxide 2.5-5%, and add oral doxycycline or minocycline for 3-4 months given the 5-6 year chronicity and likely moderate-to-severe inflammatory nature of your back and underarm acne. 1, 2

Initial Treatment Approach

The American Academy of Dermatology recommends treating back acne using the same severity-based algorithm as facial acne. 1, 2 Given your 5-6 year history with large red lesions and dark spots, this represents moderate-to-severe inflammatory acne with post-inflammatory hyperpigmentation (PIH).

Core Treatment Regimen

For the active acne:

• Oral antibiotics: Start doxycycline or minocycline (strongly recommended by the American Academy of Dermatology) for 3-4 months maximum to avoid bacterial resistance. 1, 2
• Topical retinoid: Apply adapalene 0.1% gel (available over-the-counter), tretinoin, or tazarotene nightly to all affected areas—this is the foundation of treatment. 1, 2
• Benzoyl peroxide: Use 2.5-5% formulation daily, always combined with the antibiotic to prevent bacterial resistance. 1, 2
• Fixed-combination products like clindamycin 1%/benzoyl peroxide 5% can enhance compliance. 1, 2

For the dark spots (hyperpigmentation):

• Continue the topical retinoid: This is critical—retinoids treat both acne AND hyperpigmentation simultaneously by normalizing skin cell turnover and reducing melanin deposition. 3, 4, 5
• Add azelaic acid: The American Academy of Dermatology specifically recommends this for patients with post-inflammatory hyperpigmentation, as it has comedolytic, antibacterial, and anti-inflammatory properties. 1
• Consider hydroquinone as adjunctive therapy for enhancing pigmentation improvement. 4

Critical Timing and Expectations

Start topical retinoids as early as possible—this is emphasized repeatedly in the literature because PIH is often more distressing than the acne itself, and retinoids address both simultaneously. 3, 4, 5 The active acne lesions will improve within weeks, but the dark spots take much longer to resolve—typically months. 3 Managing this expectation prevents frustration and premature treatment discontinuation.

Special Considerations for Your Case

Location matters: Back and underarm acne can be particularly challenging due to:

• Difficulty with application—consider spray formulations of benzoyl peroxide or having someone help with application. 2
• Benzoyl peroxide bleaches clothing and bedding, so wear old or white clothing when applying to these areas. 2
• The underarm location may require extra caution with irritating products due to friction and occlusion.

Darker skin types: If you have darker skin (Fitzpatrick phototypes IV-VI), you're at higher risk for PIH, making early aggressive treatment with retinoids even more important. 3, 4, 5 Retinoids have been specifically shown to reduce hyperpigmentation in patients with skin of color. 3, 6

Maintenance Phase (After 3-4 Months)

Stop the oral antibiotic after 3-4 months to minimize bacterial resistance. 1, 2

Continue indefinitely:

• Topical retinoid nightly for maintenance—this is essential to prevent recurrence. 1, 2
• Benzoyl peroxide can be continued as maintenance therapy. 1

Never stop treatment once acne clears—this is a critical pitfall. The American Academy of Dermatology emphasizes that maintenance therapy with topical retinoids is crucial to prevent relapse. 2

If Initial Treatment Fails After 3-4 Months

For persistent severe acne: Consider isotretinoin (oral retinoid) for severe, recalcitrant cases that fail standard treatment. 2

For persistent hyperpigmentation: Add chemical peels as adjunctive or second-line therapy—these can be safely performed when combined with appropriate protocols. 4

Common Pitfalls to Avoid

• Never use topical antibiotics alone—this creates bacterial resistance. Always combine with benzoyl peroxide. 1, 2
• Don't underestimate severity when scarring or hyperpigmentation is present—these warrant more aggressive treatment. 1
• Don't extend oral antibiotics beyond 3-4 months—this increases resistance risk. 1, 2
• Apply sunscreen daily—topical retinoids cause photosensitivity, especially important for exposed back areas. 2

Practical Application Tips

Use moisturizers to reduce retinoid irritation, which can itself trigger more hyperpigmentation. 3 Novel retinoid formulations like trifarotene have shown particular efficacy for both acne and hyperpigmentation across all skin types, with significant improvement in atrophic scarring (55.2% reduction at 24 weeks). 5