There are several causes for this it would need to be located if this is coming from the lungs, mouth, throat, or gastrointestinal tract. If you are not sure of where the actual blood is coming from, you should be seen by your doctor for an in person evaluation especially since there are more than one location this could be from. It may just be as simple as a sinus infection especially with you saying you blew your nose and there was blood too or a possible tumor (worst case) but without an in person exam it would be hard for me to pin point the area. If the air is dry then this too can dry our your sinus cavity which could possibly cause this.
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