What is the likely diagnosis and treatment for an itchy rash in a healthy 40‑year‑old woman who just returned from Mexico and had a recent cold?

Likely Diagnosis and Management

This is most likely cutaneous larva migrans (CLM), a self-limited parasitic skin infection acquired from contaminated sand or soil in Mexico, and should be treated with a single oral dose of ivermectin 200 mcg/kg or albendazole 400 mg daily for 3 days. 1

Clinical Reasoning

Why Cutaneous Larva Migrans is Most Likely

• CLM presents with a characteristic itchy, serpiginous (snake-like) rash that migrates 1-2 cm per day, caused by dog or cat hookworm larvae penetrating the skin 1, 2
• Mexico is endemic for CLM, as the condition has worldwide distribution with predominance in warmer, tropical and subtropical regions 1, 2
• The timing fits: CLM typically appears within days of exposure to contaminated beach sand or soil 1
• The "cold" during travel is likely unrelated to the rash, as CLM is not associated with upper respiratory symptoms 1

Key Diagnostic Features to Confirm

• Look for raised, erythematous, serpiginous (winding/snake-like) tracks on the skin, most commonly on feet, legs, buttocks, or hands 1
• Ask about walking barefoot on beaches or sitting on sand in Mexico 1
• The rash should be intensely pruritic (itchy) 1, 3
• Diagnosis is entirely clinical—no laboratory testing is required 1
• Peripheral eosinophilia may be present but is not necessary for diagnosis 1

First-Line Treatment Options

Choose either of these equally effective regimens:

• Ivermectin 200 mcg/kg as a single oral dose (cure rates 95-100%) 1

  • Preferred for convenience (single dose)
  • Well-tolerated with minimal side effects 1

• Albendazole 400 mg orally once daily for 3 days 1

  • Alternative first-line option with excellent efficacy 1
  • May extend to 7 days if multiple or extensive lesions 1

Critical Management Pitfalls

• Do not confuse persistent itching with treatment failure: Pruritus can persist for several days after successful parasite eradication due to ongoing inflammatory response 1
• Distinguish CLM from human hookworm infection (Ancylostoma duodenale, Necator americanus), which causes minimal skin symptoms but proceeds to systemic infection requiring different management 1, 2
• The zoonotic hookworm larvae causing CLM remain trapped in the epidermis and cannot complete their life cycle in humans, whereas human hookworm larvae migrate internally 2

Special Population Considerations

• Pregnancy: Ivermectin has shown no teratogenicity in limited human data, though caution is warranted; albendazole should be avoided in first trimester 1
• Breastfeeding: Both medications appear compatible based on low excretion into breast milk 1
• No dose adjustment needed for renal impairment, but safety of multiple ivermectin doses in severe liver disease is not established 1

Alternative Diagnoses to Briefly Consider

While CLM is most likely, briefly assess for:

• Cercarial dermatitis (swimmer's itch): Presents within hours of freshwater exposure with itchy maculopapular rash, but does not have the characteristic serpiginous pattern 4
• Drug reaction: The recent "cold" may have been treated with medications causing pruritus, though this typically lacks the migratory serpiginous pattern 5
• Schistosomiasis: Can cause itchy rash but typically presents with systemic symptoms (fever, headache, cough) and requires freshwater exposure 4

Expected Clinical Course

• The rash is self-limited and will resolve spontaneously in weeks to months without treatment, but treatment dramatically shortens duration and relieves symptoms 1
• Symptomatic improvement typically occurs within 48-72 hours of treatment 1
• Reassure the patient this is not dangerous and does not lead to systemic infection 2