What is the diagnosis and treatment for a one-month duration of itchy foot with redness, swelling, and slight drainage without fever?

Diagnosis and Management of Chronic Itchy Foot with Redness, Swelling, and Drainage

This presentation most likely represents tinea pedis (athlete's foot) with possible secondary bacterial infection, requiring topical antifungal therapy as first-line treatment, with consideration for bacterial superinfection given the drainage. 1, 2

Initial Diagnostic Approach

The one-month duration with itching as a primary symptom strongly suggests a fungal etiology rather than primary bacterial infection. 3 Key distinguishing features to assess:

• Fungal infection (tinea pedis) typically presents with itching, scaling, and redness, particularly between the toes or on the plantar/lateral foot surfaces 1, 2
• The presence of drainage suggests either maceration from fungal infection or secondary bacterial superinfection 3
• Absence of fever makes severe bacterial infection or diabetic foot infection less likely, though diabetic patients may not mount typical inflammatory responses 4

Critical Red Flags to Exclude

Before proceeding with simple antifungal treatment, assess for these concerning features:

• If diabetic: Immediately test for protective sensation using monofilament testing and assess for possible Charcot neuro-osteoarthropathy or diabetic foot infection 5
• Probe any visible wound with a sterile blunt probe—if bone is palpable (hard, gritty feel), osteomyelitis must be excluded 4
• Check for systemic signs: fever, rapid progression, extensive necrosis, or crepitus would indicate limb-threatening infection requiring urgent surgical consultation 4
• Assess vascular status by palpating dorsalis pedis and posterior tibial pulses—absent pulses suggest ischemia requiring vascular surgery referral 4, 5

Recommended Treatment Algorithm

For Presumed Uncomplicated Tinea Pedis:

Apply topical terbinafine twice daily for 1 week if infection is between the toes, or twice daily for 2 weeks if on the bottom or sides of the foot 1, 2

• Allylamines (like terbinafine) are more effective than azoles, with a risk ratio of treatment failure of 0.63 favoring allylamines 2
• Wash affected skin with soap and water and dry completely before applying medication 1
• Wear well-fitting, ventilated shoes and change shoes and socks at least once daily to reduce moisture 1, 3

If Secondary Bacterial Infection is Suspected:

The presence of purulent drainage, increasing warmth, or spreading erythema suggests bacterial superinfection requiring antibiotic coverage 6, 5

• For mild bacterial superinfection without systemic symptoms, consider adding topical antibiotics while continuing antifungal therapy 3
• If moderate cellulitis is present (deeper involvement, more extensive erythema), oral antibiotics such as amoxicillin-clavulanic acid are indicated 5

When to Obtain Imaging

Plain radiographs of the foot should be obtained if:

• The wound has been present for many weeks, is deep, located over a bony prominence, or shows visible bone 4
• There is a "sausage toe" appearance with erythema and swelling 4
• The patient is diabetic with any open wound or drainage 4

MRI is the most accurate imaging for detecting osteomyelitis and deep soft tissue infection, but is not first-line unless plain films are abnormal or clinical suspicion remains high after initial treatment 4, 5

Follow-Up Strategy

Reassess at 48-72 hours for clinical improvement—if no improvement is seen, reconsider the diagnosis and check any culture results 6, 5

• If symptoms worsen or fail to improve with antifungal therapy, consider alternative diagnoses including bacterial infection, contact dermatitis, or rare entities like mycetoma (though this typically presents with nodules and discharging sinuses with granules) 7, 8
• For refractory infections not responding to topical therapy, refer to podiatry for further evaluation 3

Common Pitfalls to Avoid

• Do not dismiss drainage as purely fungal—bacterial superinfection is common and may require concurrent antibiotic therapy 3
• Do not delay evaluation in diabetic patients—they may have minimal pain due to neuropathy but still have serious infection 4, 5
• Do not assume absence of fever excludes serious infection in diabetic or immunocompromised patients 4
• Ensure adequate treatment duration—premature discontinuation leads to recurrence 1, 2