Foot eczema is a common skin condition, yet it is often misdiagnosed and can lead to isolation for patients. Confined to the darkness of shoes, this anatomical area is exposed to some of the harshest constraints of the human body: weight pressure, constant mechanical friction, heat, and moisture.
The clinical outcome is often painful: erythema (redness), severe pruritus (itching), scaling, or the appearance of vesicles. These symptoms disrupt sleep and quality of life, in both adults and children.
A frequent confusion persists between eczema and fungal infections (“athlete’s foot”) or psoriasis. Yet an accurate diagnosis is essential: applying antifungal treatment to eczema can worsen inflammation. This article details the physiological mechanisms behind this skin imbalance, helps identify common allergens (such as Chromium VI), and offers an appropriate skincare routine to restore the skin barrier.
Soothe itching without irritating the skin
Why is the skin of the feet so vulnerable to eczema?
To treat it effectively, it is essential to understand the specific physiological environment of the foot, which presents three characteristics that make the skin vulnerable to eczema:
- Natural xerosis (dryness): The soles of the feet lack sebaceous glands. They therefore do not produce sebum, the lipid film that naturally protects the skin from dehydration. Without external support, the skin barrier weakens and cracks.
- An environment prone to maceration: Conversely, this area has a very high density of sweat glands (600 per cm²). In a closed environment (shoes), moisture raises skin pH, which promotes inflammation and bacterial proliferation (notably Staphylococcus aureus).
- Accumulation of allergens: The stratum corneum is naturally thick to withstand walking. However, this thickness can trap chemical substances found in shoes (glues, dyes), keeping them in prolonged contact with immune cells.
What are the causes and triggering factors of foot eczema?
Foot eczema is not contagious. It is an inflammatory reaction often resulting from the combination of genetic predisposition and external aggressions.
1. Atopic predisposition and impairment of the skin barrier
In individuals with atopic dermatitis, the skin barrier is defective. It allows irritants and allergens to penetrate, triggering an excessive immune response. This predisposition explains the chronic nature of symptoms and frequent recurrences.
2. Sweating and occlusion
Hyperhidrosis (excessive sweating) is a major aggravating factor. Moisture retained in poorly breathable footwear creates an occlusive effect. This maceration weakens the epidermis and facilitates the onset of dyshidrosis.
3. Mechanical friction
Weight-bearing areas (heel, metatarsals) and friction zones (top of the toes) are the most exposed. Inappropriate footwear or synthetic socks maintain mechanical irritation which, over time, causes skin thickening (hyperkeratosis) and fissures.
4. Contact allergens (materials)
Allergic contact eczema is common on the feet. The most frequent allergens include:
- Chromium VI: Used in the tanning of most leathers.
- Glues and resins: Present in sole assembly.
- Nickel and cobalt: Found in metal eyelets and certain dyes.
- Textile dyes: Especially dark dyes (blue, black) in synthetic socks.
5. Systemic factors: Stress and smoking
- Stress: A recognized trigger for dyshidrosis flare-ups, as the nervous system and the skin are closely linked embryologically.
- Smoking: In adults, active smoking is a proven aggravating factor for hand and foot eczema (dyshidrosis and palmoplantar pustulosis), impairing microcirculation and delaying healing.
What are the symptoms of foot eczema and how does it evolve?
Foot eczema is a dynamic condition: it does not always present in the same form and often evolves through successive flare-ups. Identifying these stages helps adapt the therapeutic response.
1. Early signs: erythema and discomfort
The initial stage manifests as localized inflammation. Red areas (erythema) appear on the sole, heel, lateral edges, or between the toes.
- Sensation: The skin becomes warm to the touch, with a feeling of tightness.
- Warning sign: Pruritus (itching) is the key clinical symptom. Moderate during the day, it tends to intensify in the evening and at night.
2. Acute phase: vesicles and “dyshidrosis”
In many patients, inflammation progresses to a vesicular form specific to the hands and feet: dyshidrosis.
- Visual appearance: The eruption of tiny blisters (“vesicles”) filled with clear fluid, often compared to tapioca grains embedded under the epidermis.
- Pain: Itching becomes intense and may be replaced by a burning sensation.
- Risk: Scratching is a trap. It ruptures the vesicles, exposes raw skin, and opens the door to bacterial superinfection.
3. Drying phase: scaling and cracks
After a few days, vesicles dry out naturally or rupture. The skin then begins to peel (scaling), sometimes in sheets or fine collars, revealing new, red, extremely fragile skin. If the skin is not intensively nourished, fissures or cracks may form in pressure areas (heel), making walking painful.
4. Chronic stage: lichenification
If flare-ups recur without sufficient remission or scratching becomes chronic, the skin thickens, becomes rough, dry, and marked: this is lichenification. These thick plaques require specific care to soften the stratum corneum.
