Background: Hyperhidrosis is defined as excessive sweating which can be primary or secondary. Data about the prevalence of primary hyperhidrosis are scarce for northern Europe. Objective: Our aim was to investigate the prevalence of hyperhidrosis focusing on its primary form and describe the quality of life impairments for the affected individuals. Methods: Five thousand random individuals aged 18-60 years in Sweden were investigated. The individuals' addresses were obtained from Statens personadressregister, SPAR, which includes all persons who are registered as resident in Sweden. A validated questionnaire regarding hyperhidrosis including the Hyperhidrosis Disease Severity Scale (HDSS) and 36-item Short Form (SF-36) health survey was sent to each individual. The participants were asked to return the coded questionnaire within 1 week. Results: A total of 1,353 individuals (564 male, 747 female and 42 with unspecified gender) with a mean age of 43.1 ± 11.2 years responded. The prevalence of primary hyperhidrosis was 5.5%, and severe primary hyperhidrosis (HDSS 3-4 points) occurred in 1.4%. Secondary hyperhidrosis was observed in 14.8% of the participants. Our SF-36 results showed that secondary hyperhidrosis causes a significant (p < 0.001) impairment of both mental and physical abilities while primary hyperhidrosis impairs primarily the mental health (p < 0.001). Conclusion: Hyperhidrosis affects individuals in adolescence as a focal form while occurring as a generalised form with increasing age. Further, the prevalence of primary hyperhidrosis described in our study is comparable to other studies from the western hemisphere. While secondary, generalised hyperhidrosis impairs both physical and mental aspects of life, primary hyperhidrosis, with the exception of severe cases, mainly affects the mental health.