Lyme serology or even PCR (polymerase chain reaction) tests are by no means always necessary when it comes to diagnosing skin borreliosis and initiating treatment. In typical erythema migrans, the motto is: do not search for antibodies, but treat directly. Early antibiotic therapy may even prevent seroconversion. Serologies for therapy or progression control are useless. Prof. Dr. Martin Hartmann, Heidelberg, spoke about the place of serology in Lyme disease diagnostics at the 2017 Annual Meeting of the SGDV.