Background: Reversible cerebral vasoconstriction syndrome (RCVS) is an important differential diagnosis of singular or recurrent thunderclap headache. Prognosis is generally good, however complications of the transient segmental vasospasms of cerebral arteries such as stroke, subarachnoidal hemorrhage and brain edema may worsen the clinical outcome. Although the exact pathomechanism is still unclear, various vasoactive substances and conditions (e.g. post partum) have been identified as triggering RCVS. Cases: We report on the clinical course and management of two cases of typical RCVS that were associated with two different precipitants previously not described: A gastrointestinal infection and isoflavones, which are phytoestrogens used for menopausal vasomotor symptoms. Discussion: In the case of gastrointestinal infection, either systemic inflammatory processes might lead to disturbances of vascular tone, or the repetitive vomiting that resembles Valsalva manoeuvers known to trigger RCVS. In the case of isoflavone intake, it may be their estrogenic potential that induces dysregulation of cerebral arteries, a mechanism known from other states of hormonal change such as post-partum angiopathy. However, the association of both precipitating factors with RCVS in our two cases is not a proof for a causal relationship, and there may have been additional potential triggers for RCVS. Conclusion: In patients with (gastrointestinal) infection and concomitant thunderclap headache, RCVS should be considered as an important differential diagnosis due to its major complications. Since RCVS may be triggered by various vasoactive substances, taking the medical history should always include over-the-counter drugs and dietary supplements (such as the isoflavones) beside the regular medication.