https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7181938/
https://www.cdc.gov/eid/article/26/5/19-0994_article
> Disposable medical masks (also known as surgical masks) are loose-fitting devices that were designed to be worn by medical personnel to protect accidental contamination of patient wounds, and to protect the wearer against splashes or sprays of bodily fluids (36). There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza.
> We did not consider the use of respirators in the community. Respirators are tight-fitting masks that can protect the wearer from fine particles (37) and should provide better protection against influenza virus exposures when properly worn because of higher filtration efficiency. However, respirators, such as N95 and P2 masks, work best when they are fit-tested, and these masks will be in limited supply during the next pandemic. These specialist devices should be reserved for use in healthcare settings or in special subpopulations such as immunocompromised persons in the community, first responders, and those performing other critical community functions, as supplies permit.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/
> Penetration of cloth masks by particles was almost 97% and medical masks 44%. This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.
https://www.osha.gov/Publications/OSHA3767.pdf
> The purpose of a facemask, when worn by a patient suspected or confirmed with an illness such as influenza or tuberculosis, is to reduce the amount of large infectious particles released as the patient talks, sneezes, or coughs; this limits their concentration in the room air and reduces the infection risk to others who are present.
> However, facemasks by design do not seal tightly to the wearer’s face. Therefore, they allow unfiltered air to easily flow around the sides of the facemask into the breathing zone and respiratory tract of the wearer. In addition, the materials used for facemasks are not regulated for their ability to filter particles and are known to vary greatly between models. This makes it possible for small particles to pass through or around the facemask and be inhaled by the wearer. This is why they are not considered respiratory protection— facemasks do NOT provide the wearer with a reliable level of protection from inhaling smaller particles, including those emitted into the room air by a patient who is exhaling or coughing, or generated during certain medical procedures.
Also eyes are an entry point too:
https://www.biorxiv.org/content/10.1101/2020.05.09.086165v1....
> Conclusions: Together, these results indicate that ocular surface cells including conjunctiva are susceptible to infection by SARS-CoV-2, and could therefore serve as a portal of entry as well as a reservoir for person-to-person transmission of this virus. This highlights the importance of safety practices including face masks and ocular contact precautions in preventing the spread of COVID-19 disease.
EDIT: Why is everyone downvoting me? I literally shared multiple studies which state "There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure."