What are the causes and treatments for little red skin bumps?

Little Red Skin Bumps: Diagnostic Approach and Treatment

The most common causes of little red skin bumps include impetigo, folliculitis/furuncles, urticaria pigmentosa (mastocytosis), erythema multiforme, and viral exanthems, with treatment directed at the specific underlying cause identified through lesion morphology, distribution, and associated symptoms. 1, 2

Diagnostic Algorithm Based on Lesion Characteristics

Target or Iris-Shaped Lesions

• Look for three-zone configuration: central dark papule/vesicle, pale middle zone, and erythematous outer halo that remains fixed for at least 7 days 2
• This pattern indicates erythema multiforme, typically triggered by HSV infection (appearing 10 days post-infection) or Mycoplasma pneumoniae 2
• Distribution favors extremities and limbs over trunk 2
• Critical distinction: Unlike urticaria, these lesions do NOT resolve within 24 hours 2

Vesicles, Pustules, and Crusted Lesions

• Nonbullous impetigo: Papules evolving to vesicles, then pustules with thick honey-colored crusts over 4-6 days, primarily on face and extremities 1
• Bullous impetigo: Flaccid bullae with clear-to-turbid fluid, leaving thin brown lacquer-like crusts 1
• Treatment: Topical mupirocin for localized disease; oral antibiotics (cephalexin, dicloxacillin) for extensive involvement 1, 3
• Caused by Staphylococcus aureus or Streptococcus pyogenes 1, 3

Red-Brown Macules, Papules, or Nodules with Positive Darier's Sign

• Urticaria pigmentosa (mastocytosis): Red to brown to yellow lesions measuring few mm to 1-2 cm, appearing in 70-90% of pediatric mastocytosis cases 1
• Pathognomonic finding: Wheal and flare formation after stroking lesions (Darier's sign) 1
• Distribution: trunk and extremities, sparing palms, soles, scalp, and sun-exposed areas 1
• Onset timing: 80% develop by 6 months of age; lesions appearing before age 10 typically resolve by puberty 1
• Associated symptoms: flushing (36%), pruritus, dermatographism, rarely wheezing or syncope 1

Painful, Tender, Fluctuant Nodules

• Furuncles (boils): Hair follicle infections extending into subcutaneous tissue with central pustule and emerging hair 1
• Carbuncles: Coalescent inflammatory masses with multiple drainage points, common on posterior neck in diabetics 1
• Treatment: Incision and drainage is primary therapy; moist heat for small furuncles 1
• Antibiotics only needed for multiple lesions, extensive cellulitis, or systemic symptoms 1

Flexural or Palmar Distribution

• Consider atopic dermatitis or contact dermatitis: Erythematous plaques in antecubital fossae or palms 4
• First-line treatment: Urea-containing moisturizers (5-10%) for barrier restoration 4
• Avoid triggers: frequent hot water washing, skin irritants, excessive sun exposure 4

Critical Pitfalls to Avoid

Do Not Confuse with Stevens-Johnson Syndrome/TEN

• SJS/TEN features: Flat atypical targets or purpuric macules with epidermal detachment and positive Nikolsky sign 2
• EM features: Raised typical targets, predominantly on extremities, drug-related less common 2
• SJS/TEN has higher mortality; EM has better prognosis 2

Document Lesion Evolution

• Photograph and mark borders to track progression versus migration over 24-48 hours 2
• Fixed lesions (≥7 days) suggest EM; migratory lesions suggest urticaria 2
• This distinction is critical for accurate diagnosis 2

Consider Infectious Triggers Requiring Specific Testing

• Mycoplasma pneumoniae: May present with predominantly mucous membrane involvement in children 2
• HSV: Most common trigger for erythema multiforme 2
• Streptococcal infection: Consider if sandpaper-textured rash present (scarlet fever) 5

Treatment Approach by Diagnosis

For Bacterial Infections (Impetigo, Furuncles)

• Topical therapy: Mupirocin for localized impetigo avoids systemic side effects 3
• Systemic therapy: Penicillinase-resistant penicillins, first-generation cephalosporins, or amoxicillin/clavulanate for extensive disease 1, 3
• Penicillin allergy: Cephalosporins if no severe allergy history 5

For Mastocytosis

• Symptomatic management: Antihistamines for pruritus and flushing 1
• Reassurance: Most pediatric cases resolve by puberty 1
• Avoid triggers: Friction, temperature extremes, certain medications 1

For Erythema Multiforme

• Treat underlying trigger: Antiviral therapy for HSV-associated cases 2
• Supportive care: Lesions typically self-resolve 2
• Histopathological confirmation when clinical diagnosis uncertain 2