Hello Welcome to healthcaremagic I have gone through your query & appreciate your concern Blood in sputum can be a worrisome symptom. The causes for blood in sputum include 1 Forceful cough or sneezing leading to erosion of the respiratory tract can cause bleeding. 2. This might be due to bleeding from mouth area such as gum which came out when you cough. 3.Upper respiratory tract infection such as bronchitis. 4. This may also be symptom of lung infection such as pnemonia, tuberculosis etc. If its a single episode and there is no fever or persistent cough then there is no need to investigate. However, if this recurs or there is associated fever and other symptoms tests including blood counts, chest x ray, sputum should be done. Hope this information helps.