Which of the following is NOT a common symptom of respiratory illnesses like Covid-19?

Skin rash is not a common symptom of respiratory illnesses such as Covid-19. Respiratory issues tend to primarily present with symptoms that directly affect the system involved in breathing. Common symptoms include fever, which indicates an infection or inflammation, shortness of breath, which reflects the respiratory distress that can occur, and coughing, which is a reflex that helps clear the airways of irritants and is often a response to respiratory infections. While Covid-19 can occasionally present with a skin rash in some patients, this is much less common compared to the other symptoms directly linked to the respiratory system. Therefore, skin rash stands out as an uncommon symptom associated with these types of respiratory illnesses.