Pruritus of the Foot: A Dermatological and Systemic Overview

Cutaneous Causes of Pedal Pruritus

Localized irritation and inflammation of the skin on the foot can lead to pruritus. Common causes include:

Xerosis (Dry Skin): Inadequate hydration of the stratum corneum.
Contact Dermatitis: Allergic or irritant reactions to substances such as soaps, lotions, shoe materials (leather, rubber, adhesives), or plant allergens.
Athlete's Foot (Tinea Pedis): Fungal infection typically caused by dermatophytes (e.g., Trichophyton, Epidermophyton, Microsporum). May present with scaling, fissuring, and erythema, especially between the toes.
Dyshidrotic Eczema (Pompholyx): Characterized by small, intensely pruritic vesicles on the soles, toes, and sides of the feet.
Scabies: Infestation by the mite Sarcoptes scabiei, presenting with intense nocturnal pruritus and small, burrow-like lesions. Often affects the interdigital spaces.
Insect Bites: Reactions to bites from mosquitoes, fleas, mites, or other insects.
Plantar Psoriasis: Scaling, erythematous plaques on the soles of the feet.
Cellulitis/Erysipelas: Bacterial skin infection of the deeper layers of the skin, may involve pruritus alongside pain, warmth and redness.

Pruritus of the foot, especially if generalized or accompanied by other symptoms, may indicate an underlying systemic condition:

Cholestatic Liver Disease: Elevated levels of bile acids in the blood can cause generalized pruritus.
Chronic Kidney Disease: Uremic pruritus can affect any part of the body, including the feet.
Diabetes Mellitus: Peripheral neuropathy and poor circulation can contribute to skin changes and pruritus.
Thyroid Disorders: Both hyperthyroidism and hypothyroidism can be associated with pruritus.
Iron Deficiency Anemia: May be associated with generalized pruritus.
Lymphoma and Leukemia: Pruritus can be a symptom of certain hematologic malignancies.
Allergic Reactions (Systemic): Reactions to food, medications, or other allergens can cause generalized pruritus.
Neuropathic Pruritus: Damage or dysfunction of the nervous system can cause localized or generalized pruritus.

Evaluation involves a thorough history, physical examination, and potentially diagnostic testing:

Medical History: Assessing for pre-existing medical conditions, medications, allergies, and family history.
Physical Examination: Visual inspection of the skin, assessment of lesion morphology and distribution.
Skin Scraping for KOH Examination: To detect fungal elements in cases of suspected tinea pedis.
Skin Biopsy: May be indicated if the cause of the pruritus is unclear or if malignancy is suspected.
Allergy Testing: Patch testing to identify potential allergens in contact dermatitis.
Blood Tests: To assess for systemic conditions such as liver disease, kidney disease, thyroid disorders, and iron deficiency.

Treatment strategies depend on the underlying cause:

Emollients: For xerosis, frequent application of moisturizers.
Topical Corticosteroids: To reduce inflammation and pruritus in eczema and dermatitis.
Topical Antifungals: For tinea pedis, examples include clotrimazole, miconazole, or terbinafine. Oral antifungals may be necessary for severe or recalcitrant infections.
Oral Antihistamines: To relieve pruritus, particularly if associated with allergic reactions.
Topical or Oral Antiparasitics: For scabies, permethrin cream or oral ivermectin.
Management of Underlying Systemic Conditions: Addressing the underlying medical condition causing the pruritus.
Avoidance of Irritants and Allergens: Identifying and avoiding substances that trigger contact dermatitis.