well if it is blood then that should be checked out but remember that a rat's snot, tears and spit are all red. so if he has a snotty nose and other breathing problems or is lethargic or just plan out of sorts then he may be sick so a vet checked would be good there too. some rats will have eye goobers and/or a slightly snotty nose when they first wake up before they give themselves a good bath. that's normal. but if the snotty nose does not go away during the day or if their are breathing sounds or if he seems more tired then usual then that would be time to take them to a vet.