Osmophobia and Odour-triggered Headaches – Review of the Literature and Main Research Centres

Abstract

T here is an important relationship between odours and primary headaches. Patients may present osmophobia during headaches and odours may trigger headache attacks. This review aimed to describe the studies on osmophobia, odour-triggered headache, the main researchers and their research centres. Publications on the relationship between odours and primary headaches were searched in 193 sovereign countries and 48 dependent territories in all continents. We consulted the PubMed database and used the descriptors: “osmophobia in [name of the country or territory]”; “odours and headache in [name of the country or territory]” and “smell and headache in [name of the country or territory]”. A total of 254 articles were found, but only 31 articles were considered relevant and composed this review. Of the 31 articles, 90.3% were cross-sectional studies, 6.5% case reports and 3.2% systematic reviews. All studies were performed on three continents: Europe (45.2%), America (32.2%) and Asia (22.6%). For the purpose of this study, North America and South America have been classed as one continent. No research was developed in Africa or Australia. More than 50.0% of the studies were conducted in Italy and Brazil. Only five authors published 38.7% of the studies. Osmophobia during headache attacks was investigated in 67.7% of studies, and odour-triggered headache in 19.3%. Studies on osmophobia and/or odour-triggered headache were carried out in several countries. They were useful in differentiating between migraine and tension-type headache. This could improve the accuracy of diagnosis of migraine compared to the current criteria.