Shoe allergy is a common form of contact dermatitis of the feet. However, it must be distinguished from other forms of foot allergy and inflammation that also occur frequently. It is a very common occurrence among children who need to be well educated about personal care in order to prevent this condition. Patch testing is the best means of accurate prognosis of shoe allergy. Personal care forms an integral part treatment of this annoying condition.

Shoe allergy agents

Irritant shoe dermatitis can be caused from regular footwear that keeps it covered and confined. The major shoe-based irritants are as follows:

• Paratertiary butylphenol formaldehyde resin, which is an ingredient of shoe glues.
• Shoe parts that consist of rubber chemicals, for instance mercaptobenzothiazole, which is a rubber element found in glues that attach layers of a shoe.
• Colophony is another component that causes shoe allergy.
• Leather components such as chromate (mainly potassium bichromate/dichromate) that is required in leather tanning. Such a leather element generally triggers a form of allergic dermatitis on the upper surface of the feet.
• Rubber cement glue residues in rubber boots.

The chemicals listed above are generally discharged in reaction to sweat in the feet and the condition is aggravated by it.

Symptoms

Clinical manifestations of shoe allergy are:

• Subacute eczematous flare-up, which is generally two-sided in occurrence. However, in some cases it may be confined to one side of the feet as well.
• Reddening of the skin of the feet.
• Flaking over the upper surface of the feet, mostly the toes. The areas between the fingers or toes (web of the feet) are not infected, as is seen in athlete’s foot (tinea pedis). The soles are also spared, since they are tougher, thicker and hence more resilient to irritants.

Diagnosis

Shoe allergy can be apparently identified by means of the location and shape of its clinical appearance. Generally, the outline of inflammation corresponds exactly to the lining of the shoe that one wears regularly. The location of the dermatitis, which is obviously the area that is covered by the shoe, is a key diagnostic indicator.

Foot dermatitis that cannot be managed with treatment should be patch tested for shoe dermatitis. Patch testing is vital to verify the condition. A conventional patch test procedure consists of specialized shoe patch testing trays. It should be conducted by a trained professional.

Here is an overview of the step-by-step patch test procedure:

• Collect parts of the shoe that covers the affected spot.
• Cut the parts into 1-inch square pieces and round off the edges.
• Separate the portions that have adhesives (glues) on them.
• Separate all layers for patch test.
• Dampen each layer with water.
• Attach each piece to the upper outer arm with a tape.
• Then conduct the patch test.

Differential Diagnosis

Shoe allergy should not be confused with other types of foot dermatitis. The foot conditions that should be excluded are:

• Fungal infections.
• Psoriasis, which is a skin problem characterized by red scaly patches.
• Atopic dermatitis, which is another common cause of foot eruptions.
• Sweaty sock dermatitis is a common occurrence in children, which is caused by excess sweating of the feet. Its clinical presentation includes scattered dryness accompanied with cracks on the toes, webs, and soles of the feet. The affected location often becomes eczematous and is confused with shoe allergy.
• At times there are eruptions in the weight bearing regions of the soles of the feet that are traced to dermatitis caused by the inner lining of shoes, shoe pads, shoe adhesives and rubber chemical components of the shoe. Though this may apparently seem like shoe dermatitis, this may be deceptive. The real cause can be contact allergy due to use of some medication.

How to avoid shoe allergy

Individuals who suffer from shoe allergy must follow a personal hygiene and care routine apart from treatment with medication.

The precautionary measures are:

• Patients should control perspiration. In fact, successful control of sweating can make way for patients to re-use both leather shoes and shoes that include rubber cement.
• One should not wear dirty socks. As a rule, they should be changed at least once a day.
• Patients should frequently sprinkle an absorbent powder on the feet.
• Patients can apply the antiperspirant called aluminum chloride hexahydrate in a 20% solution (Drysol) at bedtime.
• Patients who have shown an allergy to rubber and chrome could opt for vinyl instead.
• Inflammation of the soles of the feet can sometimes be managed effectively by placing guards, such as Dr. Scholl’s Air Foam Pads or Johnson’s Odor-Eaters, in the shoe.