Primary hyperhidrosis is idiopathic focal sweating; triggers may include emotions (eg, anxiety), physical activity, heat, and spicy food. Pathophysiology is not fully understood but is thought to result from neurogenic overactivity of sweat glands involving both the sympathetic and parasympathetic pathways. Secondary hyperhidrosis is usually generalized and is associated with an underlying medical condition (eg, metabolic disorder, neurologic condition, infection, or malignancy) or medication use. Primary hyperhidrosis occurs in both children and adults. It often begins in teenage years. It is less common in elderly individuals. It is estimated to affect between 1% and 3% of the population. A positive family history is common.
The 3 main areas of the body that are affected in primary hyperhidrosis are the palms, feet, and axillae. Prepubescent children with this condition tend to present with palmoplantar hyperhidrosis, since the axillary glands are not fully developed until after puberty. After puberty, axillary hyperhidrosis is the most common presentation. In addition to the palms, feet, and axillae, affected body regions include the scalp, face, and inframammary and inguinal folds.
The following diagnostic criteria have been proposed for primary focal hyperhidrosis: focal, visible, excessive sweating that lasts at least 6 months, has no underlying cause, and matches at least 2 of the following characteristics:
- Involvement is bilateral and symmetric
- Impairs daily activities
- Episodes occur at least once per week
- Onset is before age 25
- The patient has a positive family history
- Symptoms cease during sleep
Concomitant dermatological conditions that may be present include eczematous dermatitis, dermatophytosis, pitted keratolysis, and verrucae.