Exposure to feather-filled bedding may be a cause of hypersensitivity (HP) pneumonitis and idiopathic pulmonary fibrosis, according to a study led by the Pneumology Research Group of the Vall d'Hebron Research Institute (VHIR) and the Pulmonology Service of the Vall d'Hebron University Hospital. The authors recommend that, in the event of a case with this disease, an in-depth clinical study should be required to determine its cause. The article was published in https://www.archbronconeumol.org/es-hypersensitivity-pneumonitis-idiopathic-pulmonary-fibrosis-articulo-S030028961930609X" Arch Bronconeumol.HP is an inflammatory reaction caused by exposure to certain antigens, such as those present in birds' feathers. This reaction presents some challenges at the time of diagnosis, as it is often based on analysing whether there has been exposure to factors that are known to cause this inflammation. To date, however, no study has systematically analysed contact with avian antigens in household feathers present, for example, in duvets or feather pillows. There are some reports of patients with HP induced by this bedding, and a recent study by the same group (Lancet Resp Med 2013) found that at least 43% of patients diagnosed with idiopathic pulmonary fibrosis had chronic HP, half of which due to hidden exposure to feathers on bedding."Our main goal was to raise awareness of pulmonary hypersensitivity caused by exposure to feather-filled bedding. This is the first prospective study, and the largest to date, of patients with HP attributable to exposure to hidden feathers at home" says Dr. Ferran Morell, Ombudsman of the VHIR since 2014, pulmonologist, researcher and founder and head of the pulmonology service at Vall d'Hebron Hospital in the period 1995-2014, and promoter, organizer and coordinator of the first successful lung transplant of the State. The study is prospective and has been done by analysing patients diagnosed over a period of ten years.The results of this study found that chronic HP was the most common form of presentation (67%). Among the 127 patients diagnosed with HP, the condition was attributed to feathers on bedding in 33 (26%). Of these, 11 had an acute condition (33%) and 22 a chronic condition (67%).Dr Morell adds that "until recently, the presence of hidden feathers in the home was not considered a cause of HP, so in some cases both pneumonitis and pulmonary fibrosis (called idiopathic) in which we do not know the etiology, the disease may have been secondary to this exposure. These patients should be carefully analysed to see if this may be the source".