Sometimes i get blood in the mucous when i sneeze or in the post nasal drip. what may casue it or what may be the reason?

Nasal saline/M.D.: It is important to see your doctor to rule out other causes of nasal, throat or lung bleeding. A TB tests to rule out TB exposure or infection. Examination of the nostrils and throat may provide information about the source. Your doctor may recommend nasal saline spray, a decongestant to reduce post nasal drip. Allergies can also be treated, and avoidance of dust/smoke/pollen may help.

Nosebleeds: From irritated nasal mucosa . Also using nasal spray incorrectly can cause nosebleeds, sore throat and headaches. When ready to spray the left nostril, tilt the tip pointing towards the left ear with your right hand and vice versa. Blowing your nose hard can cause nosebleeding, too.You can apply ointment to your nostril after nasal wash to keep them moist. See your doctor, if worst.

Burst blood vessel: It is likely that you simply have a burst blood vessel, which can be common with sneezing or allergic rhinitis. If, however, you are having severe or prolonged bleeding, or bleeding from other sites (such as gums), please see your primary care provider. If necessary, he or she could refer you, based on his or her assessment.

Blowing too hard: If you pick or blow your nose too often and hard, nosebleed can occur. If you have been aiming the nasal spray (cortisone ?) towards the center instead of the outside direction in the nose, this can also cause nosebleeds especially if the nasal septum is crooked. If this persists, talk to your doctor about it but i would not be too concerned if this occurs only briefly and occasionally.