Black Spots on Arms: Causes from Sun Damage to Medical Conditions

Dark spots on arms (hyperpigmentation) have diverse etiologies:

1. Solar Lentigines (Sun/Age Spots)

• UV‑induced melanocyte hyperplasia.
• Light brown to black, 2–20 mm, on sun‑exposed sites (forearms, hands).
• Benign; increase with age/cumulative UV.

2. Post‑Inflammatory Hyperpigmentation (PIH)

• After acne, eczema, burns, cuts, insect bites.
• Darker skin types more prone.
• Fades slowly (months–years) with sun protection.

3. Drug‑Induced

• OCPs, HRT, antimalarials (chloroquine), amiodarone, tetracyclines, chemotherapeutics.
• Often diffuse or localized; may reverse after discontinuation.

4. Medical Conditions

• Acanthosis Nigricans: Velvety hyperpigmentation (axilla, neck) – insulin resistance.
• Addison’s Disease: Generalized + palmar creases, knuckles – ACTH/MSH excess.
• Hemochromatosis: Bronze skin – iron deposition.
• Porphyria Cutanea Tarda: Photosensitivity, blisters, hyperpigmentation on hands.

5. Melanoma Warning Signs (ABCDE)

• Asymmetry, Border irregular, Color variation, Diameter >6 mm, Evolving.
• New or changing spot → dermatologist urgently.

Management

• Broad‑spectrum SPF 30+ daily.
• Topical: hydroquinone (4%), retinoids, azelaic acid, vitamin C, niacinamide, cysteamine.
• Procedures: chemical peels, laser (Q‑switched Nd:YAG, fractional), IPL.
• Treat underlying condition (insulin resistance, iron overload).

Any suspicious lesion—biopsy. Early melanoma detection saves lives.