• Impetigo (bacterial): topical mupirocin for localized; oral antibiotics (cefalexin/flucloxacillin) for widespread
• Skin allergy/eczema (inflammatory): avoid triggers, topical corticosteroids, antihistamines, emollients
• Scabies (parasitic): permethrin 5% cream (whole body), treat all close contacts simultaneously

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Infected Impetigo vs Skin Allergy (Atopic/Contact Dermatitis) vs Scabies: Management

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1. INFECTED IMPETIGO

What it is

Clinical features (to distinguish)

Treatment

• Mupirocin 2% ointment TID x 5 days - drug of choice; effective against MSSA, MRSA, and GABHS; as effective as oral antibiotics for localized impetigo
• Alternatives: retapamulin, fusidic acid, ozenoxacin (bacitracin also used)

Note: In children <6 weeks, treat more aggressively. Rule out HSV with PCR if any suspicion.

Key complications to watch for

• Post-streptococcal glomerulonephritis (AGN): 2-5% of streptococcal impetigo cases (10-15% with nephritogenic strains like M-type 49, 55, 57, 60). Importantly, early treatment does not prevent AGN.
• Recurrent MSSA impetigo: culture anterior nares; treat carrier state with intranasal mupirocin BD, or 10-day rifampin + dicloxacillin (MSSA) or TMP-SMX (MRSA).

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2. SKIN ALLERGY - Atopic Dermatitis / Contact Dermatitis

What it is

Clinical features (to distinguish)

Treatment

• Avoid triggers, harsh soaps, irritants, and known allergens
• Moisturize within 2 minutes of bathing using plain petrolatum (Vaseline), Aquaphor, or Eucerin cream

Ointments are more effective than creams but creams are acceptable for patient preference.

• Prednisone taper over 3 weeks: adults 40-60 mg/day, children 1-2 mg/kg/day (max 40 mg/day)

• Oral antihistamines (diphenhydramine, hydroxyzine) - especially for nighttime pruritus
• Topical antihistamines have limited benefit; calamine lotion is soothing

• Tacrolimus 0.03-0.1% or pimecrolimus 1% - for face/intertriginous areas to avoid steroid atrophy

• Dupilumab (anti-IL-4Ra) - approved for adults and children; targets Th2 pathway

• Presents with increased crusting, exudates, weeping
• Treat with cephalexin or dicloxacillin orally
• This is a critical distinction - eczema with superinfection needs both antibiotic AND continued anti-inflammatory therapy

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3. SCABIES

What it is

Clinical features (to distinguish)

• Pruritus worse at night (key distinguishing feature)
• Burrows (pathognomonic) - serpiginous linear tracks, best found at finger webs, wrists, waist, groin, scrotum/penis
• Distribution: interdigital spaces, wrists, ankles, axillae, umbilicus, genitalia; in infants/young children the head is also involved
• Pruritic nodules around axillae, umbilicus, or penis/scrotum are highly suggestive
• Other household members often have similar symptoms

Treatment

• Permethrin 5% cream - Apply from jawline to toes (include full head/neck in infants); leave on 8-14 hours overnight; wash off. Repeat in 1 week. Effective against mites AND eggs.
  • Infants <2 months: not approved; use precipitated sulfur 5-10% in petrolatum
  • Pregnancy/nursing: permethrin is preferred over alternatives

• Oral ivermectin 200 mcg/kg - Single dose for common scabies (Cochrane review: as effective as permethrin). Not ovicidal, so give 2 doses 7-14 days apart.
  • Crusted scabies requires 3-7 doses over 8-30 days + repeated topical permethrin + keratolytic (6% salicylic acid to debulk crusts)
  • Not FDA-approved for scabies; not established in children <15 kg or in pregnancy

• Crotamiton 10% cream/lotion
• Lindane lotion - last resort only (safety concerns, neurotoxicity risk)

• Oral antihistamines
• Mid-potency topical corticosteroid creams
• Calamine lotion, menthol/methyl salicylate products

• Machine-wash ALL clothing, bed linens, and towels in hot water
• Items that cannot be washed: dry clean, hot dryer x 15 min, or seal in bag x 1 month
• Clean other household surfaces

• Treat ALL household members and close contacts simultaneously even if asymptomatic - failure to do this is the most common cause of recurrence

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COMPARISON TABLE: Key Differentiators at a Glance

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SPECIAL NOTE: Overlapping Presentations

• Eczema predisposes to impetigo (broken skin barrier allows bacterial entry)
• Scabies excoriations commonly become impetiginized
• Post-scabies pruritus can be misdiagnosed as persistent eczema
• The itch-scratch cycle of eczema can look like scabies if distribution is atypical

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Best Time to Take Calcium Supplements

Step 1 - Know Your Supplement Type (This Changes Everything)

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Step 2 - Dose Matters More Than Clock Time

• The body absorbs no more than 500 mg at one time efficiently
• If your daily dose is 1000 mg, split it into two doses taken at separate meals
• Taking a large dose all at once wastes most of it

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Morning vs Evening - What's Better?

• Pairs naturally with Vitamin D-rich breakfast foods (eggs, fortified milk, fatty fish) - Vitamin D significantly enhances calcium absorption
• Avoids potential interference with sleep (some people get GI discomfort at night)
• Avoids overlap with evening medications

• You take medications in the morning that interact (see below)
• You skip breakfast regularly
• You prefer it with dinner

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What to AVOID Taking at the Same Time

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What HELPS Absorption

• Vitamin D (D3 preferred) - the most important co-factor; take together
• A small amount of healthy fat - helps vitamin D (fat-soluble) which in turn helps calcium
• Spreading doses through the day - mimic how dietary calcium naturally works
• Adequate stomach acid - reason carbonate needs food, citrate doesn't

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Practical Summary by Scenario

Note on kidney stones: Dietary calcium taken with meals actually reduces oxalate stone risk by binding oxalate in the gut. But calcium supplements taken away from meals may increase risk. This is one case where timing with food is especially important, as noted in the National Kidney Foundation Primer on Kidney Diseases, 8e.

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