What causes a rash on the feet and how is it treated?

Rash on Feet: Causes and Treatment

The most common causes of foot rash are fungal infections (tinea pedis), bacterial infections (impetigo), contact dermatitis from shoes, and eczematous conditions, with treatment directed at the specific underlying cause identified through clinical examination and simple diagnostic tests. 1, 2, 3

Primary Diagnostic Approach

When evaluating a foot rash, immediately assess for these key distinguishing features:

Fungal Infections (Tinea Pedis)

• Scaly, itchy eruption between toes (interdigital) or on soles with firm pruritic rash 1
• Look for involvement under nails, which suggests onychomycosis 1
• Confirm with 10% KOH preparation to visualize fungal elements 1, 4
• Risk factors include communal showers, shared towels, athletic activities, and macerated skin 1, 5

Bacterial Infections (Impetigo)

• Honey-crusted skin lesions characteristic of impetigo 1
• May present as erysipelas or cellulitis with erythema and swelling 1
• Nonbullous form (70% of cases) or bullous form (30%) caused by Staphylococcus aureus or Streptococcus pyogenes 2
• Risk factors include minor trauma, abrasions, insect bites, and pre-existing athlete's foot creating entry points 2

Contact Dermatitis (Shoe Dermatitis)

• Allergens in shoe components (rubber, adhesives, leather, dyes, metals) cause localized dermatitis 6
• Distribution pattern matches shoe contact areas 6
• Patch testing may be needed for confirmation 6

Eczematous/Inflammatory Conditions

• Well-demarcated erythematous plaques with silvery-white scale suggest psoriasis 7
• Check elbows, knees, scalp, and nails for additional psoriatic involvement 7
• Dry, scaly skin with fissures indicates xerotic eczema 1

Treatment by Condition

Tinea Pedis Treatment

Topical therapy for localized disease:

• 0.77% ciclopirox cream or gel twice daily for 4 weeks 1
• 1% terbinafine gel once daily for 1 week 1
• Naftifine ointment twice daily for 4 weeks 1

Oral therapy for extensive or chronic infections:

• Terbinafine is more effective than griseofulvin, curing 50% more patients 8
• Terbinafine or itraconazole for severe cases 4
• Oral antibiotics for 6 weeks if needed 1

Impetigo Treatment

For limited lesions:

• Topical mupirocin 2% ointment three times daily for 5-7 days 2

For extensive lesions:

• Oral cephalexin, TMP/SMX, or doxycycline based on susceptibility for 10 days 1, 2
• Re-evaluate if no improvement after 48-72 hours 2

Inflammatory/Eczematous Conditions

For mild inflammation:

• Hydrocortisone topical applied to affected area 3-4 times daily (for patients ≥2 years) 9
• Emollients and moisturizers to prevent xerosis 1

For psoriasis:

• Topical corticosteroids and vitamin D analogues 7
• Refer to dermatology if >3% body surface area involved or refractory 7

Prevention Strategies

Essential preventive measures for all foot rashes:

• Daily change of socks and careful drying between toes after showers 1, 2
• Wear rubber-soled flip-flops or sandals in communal showers 1, 2
• Good personal hygiene and foot powder after bathing 1
• Avoid contact with infected individuals and sharing of towels/equipment 1
• Treat underlying conditions like athlete's foot to prevent bacterial superinfection 7, 2

Critical Pitfalls to Avoid

Do not use greasy creams for basic care as they facilitate folliculitis development through occlusive properties 1

Avoid topical acne medications and retinoids without dermatology supervision, as they cause drying and irritation 1

Do not use topical steroids inappropriately as they may cause perioral dermatitis and skin atrophy 1

Avoid hot showers and excessive soap use in xerotic conditions, as they worsen dehydration 1

When to Refer

Refer to dermatology for:

• No improvement after 2-4 weeks of appropriate therapy 7
• Suspected psoriasis with >3% body surface area involvement 7
• Diagnostic uncertainty or signs of secondary infection 7
• Severe pruritus unresponsive to initial management 7