Patients affected by hereditary hemorrhagic telangiectasia (HHT) very often suffer from recurrent nosebleeds called epistaxis. There is no treatment currently available to reduce the frequency or severity of epistaxis. This research project will examine the effect of nintedanib, a capsule to be taken twice a day, on the frequency and severity of epistaxis in HHT. The study will take place at the Respiratory medicine department of the Lausanne University Hospital (Centre hospitalier universitaire vaudois, CHUV). The investigators will recruit about 48 participants with HHT, who will be divided in 2 groups. Each group will perform the same examinations and follow-up visits. The study will begin with 2 months of observation during which subjects will be asked to fill a diary to record the number and duration of epistaxis episodes. The diary will be filled daily for the entire duration of the study, i.e. 8 months. After 2 months of observation, the treatment phase will begin. Participants will take a capsule (nintedanib 150 mg or placebo) once a day for 2 weeks, then twice a day for 14 weeks. In case of intolerance at the dose of 2 capsules per day, the treatment may be reduced to 1 capsule per day. Subjects will also have to mention on the diary any blood transfusion, iron perfusion, and any symptoms they may be experiencing. Following the 16 weeks of treatment, an 8-week follow-up period will allow to observe the effects of nintedanib after the end of the treatment period, and to monitor any unexpected adverse events.