The blisters associated with dyshidrosis occur most commonly on the sides of the fingers and the palms. Sometimes the soles of the feet also can be affected. The blisters are usually small — about the width of a standard pencil lead — and grouped in clusters, with an appearance similar to tapioca.

In more-severe cases, the small blisters may merge to form larger blisters. Skin affected by dyshidrosis can be painful and very itchy. Once the blisters dry and flake off, which occurs in about three weeks, the underlying skin may be red and tender.

Dyshidrosis tends to recur fairly regularly for months or years.

The exact cause of dyshidrosis isn't known. It can be associated with a similar skin disorder called atopic dermatitis (eczema), as well as with allergic conditions, such as hay fever. Eruptions may be seasonal in people with nasal allergies.

Risk factors for dyshidrosis include:

• Stress. Dyshidrosis appears to be more common during times of emotional or physical stress.
• Exposure to certain metals. These include cobalt and nickel — usually in an industrial setting.
• Sensitive skin. People who develop a rash after contact with certain irritants are more likely to experience dyshidrosis.
• Atopic dermatitis. Some people with atopic dermatitis may develop dyshidrotic eczema.

For most people with dyshidrosis, it's just an itchy inconvenience. For others, the pain and itching may limit the use of their hands or feet. Intense scratching can increase the risk of a bacterial infection developing in the affected skin.