Dyshidrotic eczema, also known as pompholyx, is a type of eczema characterized by the presence of vesicles (small blisters) or bullae (large blisters) on the hands and feet. This is usually chronic – persistent or recurrent. These vesicles (less than 5 mm in diameter) or bullae (greater than 5mm in diameter) are not boils (abscess). Dyshidrotic eczema is not an infectious condition although it may occur in a person with a fungal or bacterial infection of the hand or feet. The rash is intensely itchy with vigorous scratching leading to rupture of blisters with cracking of the skin and fissures.
It may appear an an independent entity or occur with atopic dermatitis or contact dermatitis (allergic or primary). It may also be associated with a number of systemic, non-dermatological diseases like HIV infection. Dyshidrotic eczema may occur either on the hands or the feet or both – the palms and soles are more often affected, often with extensive involvement of the fingers when it occurs on the hand. Milder cases may resolve before vesicles rupture and therefore cracking is avoided. These cases are more likely to be noticed on the hands. Due to the psychosocial impact of this type of skin disease on the hands, many patients will seek medical attention as soon as possible. However, it may be just as common on the feet although not noticed or even reported in the early stages.
Picture from Wikimedia Commons
Causes of Dyshidrotic Eczema
The exact cause of dyshidrotic eczema is unknown. It may be seen in up to 20% of patients with persisting skin diseases, particularly the other types of eczema, as well as in patients with skin infections. Prolonged tinea pedis (athlete’s foot – fungal infection of the feet) may result in dyshidrotic eczema both on the feet and hands although the skin of the hands are not infected.
It is believed that dyshidrotic eczema is a combination of type I and type IV hypersenstivity reactions. Read more on types of allergic reactions. This is further supported by the presence of dyshidrotic eczema in asthmatics, patients with hay fever, after exposure to chemical like nickel (known sensitivity like with costume jewelry) and IV immunoglobulin infusions. It may also be seen in HIV positive patients (after asymptomatic phase) and those on highly active antiretroviral therapy (HAART).
Dyshidrotic eczema may also be seen at times of emotional stress. Although not conclusively substantiated, it is only triggered by emotional stress in people with a history of allergic conditions (personal or family history of atopy) or existing tinea pedis. Therefore pre-existing contributing factors need to be present. It is also interesting to note that monozygomatic twins are equally affected by dyshidrotic eczema which indicates a genetic component, although this may be associated with familial atopy.
In the absence of other pre-existing factors, contact dermatitis needs to be considered as it is widely associated with dyshidrotic eczema, especially in the chronic occupational setting. Food and drug-related allergies are less common but have also been noted as possible triggers of dyshidrotic eczema.