Sweating is a crucial way to reduce our body temperature, such as when doing strenuous physical activity or when in a hot environment. Hyperhidrosis is defined as excessive sweating beyond what is physiologically required or normal. It can be categorised as primary (idiopathic), secondary to other conditions, or as a side effect of some medications. Primary hyperhidrosis can affect people at any age, but often starts in early life. The diagnosis of hyperhidrosis is typically made initially on the clinical history, and this can also determine between primary or secondary hyperhidrosis. It is usually diagnosed where there is visible sweating, which interferes with daily activities and which has lasted for at least 6 months. In this podcast, Dr Roger Henderson discusses what to look for when making the diagnosis, what investigations to undertake and the range of treatments currently available.