## 4 Discussion  
Education during the COVID-19 pandemic appeared to be a special challenge for both students and teachers. In many countries, the education program was moved, wholly or partially, to the virtual world. In Poland, after the summer holiday, all students returned to their universities, starting face-to-face classes. Gathering a bigger number of people in one place created an increased risk of SARS-CoV-2 infections. Therefore, they were all obliged to wear face masks. To the best of our knowledge, our study is the first one investigating student compliance with guidelines on the correct use of face protection. Unfortunately, our results showed that adherence to all WHO criteria among the studied students was very low, with less than 1%. In a similar study carried out on the Japanese general population, [PERSON] et al. [19] reported that 23.1% adhered to those criteria. However, it is important to notice that we employed more strict rules for fulfilling the criteria, accepting only answers of \"always/nearly always\". In the Japanese study, the answer \"sometimes\" also qualified the respondents as compliant with WHO criteria [19]. This can at least partly explain the observed difference between the results of both studies. Adherence to the face mask proper usage guidelines is not an unknown problem, even among health care workers (HCW). In 2019, it was shown that only 18% of HCW involved in surgical procedures fully adhered to the Centers For Disease Control (CDC) recommendations [20]. We also noted significant relationships between self-reported skin complaints and adherence to some of the WHO guideline criteria. It is not surprising that those respondents who declared sensitive skin and face mask-induced itch were less compliant with strict covering of the nose and mouth. Sensitive skin is also an itchy condition [21]. Face mask wearing with strict attachment to the skin surface creates a specific occlusion that may contribute to an increased itching sensation [22]. Interestingly, those with the presence of facial skin disease were more prone to adhere to the criterion for replacing the mask when it dampens. This could at least partly be explained by the fact that wearing face masks was shown to exacerbate such conditions as acne, rosacea, seborrheic dermatosis [23; 24], and the respondents tried to avoid additional flare-ups caused by a wet, occlusive environment. Although the adherence to particular criteria was low, medical students showed to be more compliant with some criteria, such as strict covering of the nose and mouth with the face mask, taking off the mask properly without touching the anterior surface and replacing the mask when it dampens. Previously, during the beginning of the COVID-19 pandemic when face mask use was not mandatory and only recommended, we revealed that medical students wore face protection significantly more often than non-medical students. Moreover, medical students more commonly used single-use masks and wore face protection for longer periods of time [25]. This is not surprising, as the differences in health-related attitudes and behaviors between medical and non-medical students have been previously documented [26; 27; 28]. The criterion that non-medical students complied significantly better with was the disposure of single-use masks after their use at work. We believe that it may be caused by differences in types of university classes. Clinical practice in hospitals and the students' attendance at different wards on the same day would require the use of several masks daily. In comparison to other university classes, it is both physically and financially more difficult. We are aware of some limitations of our project. Using the employed methodology, we were unable to assess the response rate. However, such a methodology has been previously successfully used by several authors [29; 30; 2]. Using this questionnaire, we gathered information from a sample that could be representative of the Polish student population in one week (CI 95%, margin of error 2.86%).