The aim of the study was the clinical examinations of the tolerance and effect of Olbas oil on nasal mucosa in healthy volunteers during permanent 4 weeks administration. 23 healthy volunteers both sexes in the age between 20-50 were investigated. This investigations consisted of: history data, general and otorhinolaryngological examination, with particular evaluation of nasal mucosa, anterior rhinomanometry, olfactometry, saccharin translocation time, microbiological cultures, histamine nasal provocation test. Besides, each patient has follow up self evaluating chart of symptoms and adverse effect from the eyes, nose, pharynx and others. All the examined persons showed a very good tolerance of Olbas oil after 28 days of inhalation.