Skin Rash Under Arms and Breast: Causes and Treatment
The most common cause of rash in these intertriginous areas (under arms and breasts) is intertrigo—an inflammatory condition caused by moisture, friction, and heat in skin folds—though serious conditions like inflammatory breast cancer (IBC) and Paget's disease must be ruled out when the rash involves breast skin.
Critical Red Flags Requiring Immediate Evaluation
Before treating as a benign rash, you must exclude malignancy:
Inflammatory Breast Cancer (IBC)
- Look for: Erythema and dermal edema (peau d'orange/orange peel appearance) affecting at least one-third of the breast skin with a palpable border 1, 2
- Key feature: The orange peel appearance is caused by tumor emboli blocking dermal lymphatics, not true inflammation 2
- Action required: Any patient with these findings needs bilateral diagnostic mammogram with or without ultrasound immediately 1, 2
- Important: Even if imaging is normal (BI-RADS 1-3), further workup with punch biopsy is mandatory due to high malignancy risk 1, 2
Paget's Disease of the Breast
- Look for: Nipple excoriation, scaling, eczema-like changes, bleeding, ulceration, or itching of the nipple-areolar complex 1, 3, 4
- Critical pitfall: This is often misdiagnosed as benign eczema or dermatitis, delaying cancer diagnosis 1, 3
- Action required: Bilateral diagnostic mammography first, followed by full-thickness surgical biopsy or punch biopsy of the nipple-areolar complex 1, 3
- Key fact: A negative mammogram does NOT exclude Paget's disease—it can be occult on imaging 1, 3
Common Benign Causes in Intertriginous Areas
Intertrigo (Most Common)
- Inflammatory dermatitis in skin folds caused by moisture, friction, and heat
- Often secondarily infected with Candida or bacteria
- Treatment approach:
Contact Dermatitis
- From detergents, soaps, cosmetics, deodorants, or clothing 5
- Treatment:
Seborrheic Dermatitis
Practical Treatment Algorithm for Benign Rash
Step 1: General Skin Care Measures
- Avoid frequent washing with hot water 1
- Use alcohol-free moisturizers twice daily, preferably with urea 5-10% 1
- Avoid skin irritants including over-the-counter anti-acne medications, solvents, and disinfectants 1
- Apply sunscreen SPF 15 to exposed areas 1
Step 2: Topical Treatment
- Apply hydrocortisone 2.5% or alclometasone 0.05% twice daily to affected areas 1, 5
- Continue for up to 7 days; if no improvement, reassess diagnosis 5
Step 3: If Secondary Infection Suspected
- Signs: Painful lesions, yellow crusts, discharge, failure to respond to initial treatment 1
- Obtain bacterial culture 1
- Start oral antibiotics based on sensitivities for at least 14 days 1
- Consider topical antibiotics (erythromycin, metronidazole) twice daily 1
Step 4: When to Escalate
- If rash persists beyond 2 weeks despite treatment
- If any breast skin changes develop (erythema, edema, nipple changes)
- If rash worsens or spreads despite treatment
Common Pitfalls to Avoid
Never dismiss breast skin changes as "just eczema" without proper evaluation—this delays diagnosis of IBC and Paget's disease 1, 3
Do not use long-term corticosteroids as they can mask infection and worsen certain conditions 1
Avoid alcohol-containing products in intertriginous areas as they increase dryness and irritation 1
Do not use over-the-counter anti-acne medications in these areas—they are too harsh and will worsen the condition 1
If considering a short trial of topical steroids for suspected eczema near the breast, this should not delay biopsy if clinical suspicion for Paget's disease exists 3
When Dermatology Referral is Needed
- Any breast skin changes that don't clearly resolve with initial treatment
- Rash persisting beyond 2-3 weeks despite appropriate therapy
- Uncertain diagnosis after initial evaluation
- Recurrent rashes in the same location