In the univariate analysis, the factors associated with the appearance of ‘de novo’ headache were age, female sex, type of profession, use of filter mask (KN95 or FFP2), work shift, being a tobacco user, suffering from anxiety or asthma. In the multivariate analysis, the use of filter masks and the type of profession behaved as independent predictors of headache risk, while being asthmatic behaved as a protective factor. The occurrence of headache is associated with the use of a filter mask (FFP2 or KN95), OR 2.14 (95% CI 1.07 to 4.32); being a health worker, OR 6.94 (95% CI 3.01 to 16.04) or a nurse, OR 2.09 (95% CI 1.18 to 3.72) (table 3).