Foot dermatitis

What is foot dermatitis, and how common is it?

Foot dermatitis (foot eczema) is best understood as contact dermatitis of the foot: inflammation of the skin where it has touched something from outside the body, causing a red, itchy rash¹². Contact dermatitis in general is common². How often it affects the foot specifically isn't clear yet.

There are two main types. In irritant contact dermatitis the skin reacts badly to something it meets, and this is the more common type overall³. Allergic contact dermatitis is an immune reaction to substances that are usually harmless, and it often appears alongside the irritant type⁴.

Shoe dermatitis is the form triggered by allergens or irritants in footwear. It can affect people of any age, sex or background⁵.

What causes it, and who gets it?

Most foot dermatitis comes from something your skin touches regularly, often in shoes⁵. Potassium dichromate, a chemical used in processing leather, is among the most common culprits, but it isn't the only one⁵. Metals such as nickel, chromium and cobalt are among the allergic triggers of contact dermatitis, and triggers vary from person to person². Contact allergy in general is more common in women than in men⁶.

Atopy (a tendency towards allergic conditions such as eczema) is a recognised risk factor for irritant dermatitis of the hands, and is linked with a poorer outlook³. Whether the same holds for the feet isn't clear yet.

Some other foot skin problems have different causes. Pompholyx is a blistering eczema of the hands and feet. Its cause isn't clear, but fungal infection, nickel, soaps, stress and sweating may set it off or make it worse⁷. Dry, cracked heels usually come from a lack of moisture in the skin, and can be worse in open-backed shoes such as sandals⁸.

What does it feel like, how is it diagnosed, and can it be serious?

In allergic contact dermatitis the skin feels very itchy before other symptoms appear². In irritant contact dermatitis the skin may become very itchy, dry, thick and scaly, and the rash shows only where the skin touched the irritant². An irritant rash starts at the site of contact and usually doesn't spread, and it tends to peak and then begin to heal. An allergic rash can keep getting worse even after the allergen is removed³. Long-lasting hand or foot eczema can also bring soreness, cracking, fissuring (splits in the skin) and bleeding⁹.

Diagnosis starts with your history and an examination of the skin. For long-lasting foot eczema, that history covers when it began, how it has changed, and what your feet touch, including work and hobbies⁹. A full history matters because contact dermatitis can mimic other skin diseases, such as atopic dermatitis and lichen planus¹⁰. In adults with long-lasting hand or foot eczema, patch testing (putting small amounts of possible allergens on the skin to see whether it reacts) is treated as a standard part of the work-up, to rule out an allergic cause⁹¹¹.

Athlete's foot, a fungal infection, can look like eczema. It is more likely in people with diabetes, sweaty feet or a weakened immune system⁸. Pompholyx and dry, cracked heels can also look similar.

Some features mark the rash as more serious:

• Infection. Skin can become infected in both allergic and irritant contact dermatitis². Signs include a wet rash that looks red or darker and 'angry'¹², painful blisters that ooze pus or become covered in a golden crust⁷, and excessive weeping or tenderness¹³. Infection can spread.
• A rash that isn't improving, or one that comes with a fever or feeling unwell, can mean infection or that the diagnosis or treatment needs rethinking².
• Eczema herpeticum, a serious complication of eczema, can quickly become a medical emergency¹².
• Steroid creams and infection. Steroid creams can mask or spread infection, so they are generally avoided on infected skin unless given with an anti-infective or tablets for the infection¹³¹⁴⁷.
• After stopping a steroid cream, intense redness and swelling of the skin is a warning sign¹³¹⁵.
• In children, a foot rash that looks unusual or lingers is described as needing further assessment¹⁶.

What can I do first?

The simplest and most important step for shoe dermatitis is avoiding the cause⁵. Once the trigger is identified and avoided, symptoms should improve and may clear up completely¹⁵. It can help to notice whether the rash follows a particular pair of shoes, a type of sock or a cream.

Regular moisturiser is the other mainstay: avoiding the irritant, protecting the skin and using moisturising creams is the main approach to irritant dermatitis³. In people with eczema generally, moisturisers lower disease severity and reduce flares, and no single moisturiser has been shown to be better than another¹⁷. Creams containing urea can irritate skin that is broken or strongly inflamed¹⁷.

For long-lasting hand or foot eczema in adults, good skin care is an essential first step. It includes learning about skin care, changing habits, and using barrier products and soap substitutes, although support for those last two is weak⁹. Limiting contact with irritants and allergens matters too⁹. Care goes beyond creams and medicines to include avoiding causes, changing behaviours and social support¹¹. Much of this advice comes from contact dermatitis in general, the hands, or eczema in general, rather than the foot alone.

What helps if that isn't enough?

Treatment can be stepped up. The choice depends on how acute and severe the rash is, how it looks and where it is. Approaches can be combined and tailored to the person, and they don't all need to be used at once¹. Avoiding the trigger remains as important as the eczema treatment itself¹.

When contact dermatitis is severe, prescription medicines may be used for a short time, such as corticosteroids, or tablets or creams that aren't steroids².

Will it go away, and how do I stop it coming back?

Once you avoid the trigger, a contact dermatitis rash should slowly go away². Symptoms often improve and may clear completely¹⁵. It can become long-term, though². Pompholyx tends to relapse, and current treatments are limited at preventing relapses¹⁸.

For adults with long-lasting hand and foot eczema, restoring everyday function is the main goal, and clearing the skin is secondary¹¹.

Prevention rests on recognising the trigger and then avoiding or minimising contact with it¹. It helps to keep avoiding it even after the skin has settled. Regular moisturising may also lengthen the time between flares, as it does in eczema generally¹⁷.