Flammer syndrome, which has been described in literature only recently, combines two basic components: primary vascular dysregulation and symptoms not directly related to vascular function (prolonged sleep onset time, low pain threshold or specific personality traits). Some health-protective effects, such as a reduced risk atherosclerosis and metabolic syndrome, have also been noted. Flammer syndrome most often coexists with ocular diseases, normal tension glaucoma in particular, as well as with neurological disorders, such as multiple sclerosis. Diagnosis is based on a detailed physical examination; however, standardised diagnostic methods are missing. A three-component therapeutic strategy, including appropriate lifestyle, proper nutrition and pharmacotherapy in the form of magnesium preparations or low-dose calcium channel blockers, is used for Flammer syndrome. Clinical studies in 2016 and 2019 showed that multiple sclerosis patients are significantly more likely to develop typical symptoms of Flammer syndrome compared to controls. These included dizziness, low body weight, non-migraine headaches, reduced feeling of thirst, prolonged sleep onset time, and a tendency towards perfectionism. Although the aetiology of Flammer syndrome and multiple sclerosis or the causes underlying the clinical correlations between them have not been clarified so far, expanded research may contribute to better care for those at increased risk of developing multiple sclerosis, as well as improved therapy and support for patients, with consideration given to challenges that may arise from the coexistence of both diseases.