Hello, You are experiencing blood in the spit on medication for allergies. You have history of nasal congestion. Blood in the spit is seen because blood vessels can become damaged for a variety of reasons. Once the blood vessel is damaged, you may experience bleeding more frequently when blowing your nose. The scab covering the broken blood vessel during the healing process may break off causing bleeding. You may experience slight or heavy bleeding from your nose because of damage to the interior of your nasal passages. Dryness in the nose also cause a delay in the healing of broken blood vessels and result in infections and thus frequent of bleeding when blowing your nose. Picking your nose can damage blood vessels. You may experience bleeding when blowing your nose because of nasal congestion or a respiratory infection. Frequent blowing of the nose may create broken blood vessels. Try not to sneeze or cough frequently when you have a respiratory condition. Nasal congestion or respiratory infections occur from common cold, allergies, sinusitis, etc. Do not use drugs like cocaine or exposure to harsh chemicals like ammonia as they may cause damage to the blood vessels. To prevent nasal congestions, you should take steam inhalation, decongestants, antihistamines and mucolytics. Get clinically examined by an ENT, get X-ray PNS done to detect deviated nasal septum. You will be treated accordingly. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician