My Son Flew From Massachusettsand To California And Took A

My son flew from Massachusettsand to California and took a cargo ship to Alaska. He said that he has had some sort of drainage running from his nose down the back of his throat and he thinks it is blood and it has been waking him up from his sleep on the ship. he also has had some blood from his nise when he wipes it and blows it, and had a nose bleed today. What do you think it is?