IL9 and COVID-19: In detail, in the saliva of SD patients, such factors included cytokines known to be involved in the inflammatory process caused by COVID-19, such as IL-1β (SD vs. HC: p < 0.01; vs. MD: p < 0.05), IL-2 (SD vs. HC: p < 0.05), IL-6 (SD vs. HC and MD: p < 0.05), IL-8 (SD vs. HC: p < 0.001; vs. MD: p < 0.05), IL-9 (SD vs. HC: p < 0.05), and TNFα (SD vs. HC: p < 0.01).