"Rats eyes and noses release a red mucus from them.
This Red discharge can come from the rats eyes or nose.
It is called Porphyrin, it is not blood.
It looks a light reddish color, while blood is a dark red color.
It is produced in the Porphyries glands behind the rat's eyes.
Overproduction of this discharge can be caused by stress or illness.
Porphyrin discharge can be increased if your rat has breathing trouble, pneumonia or Mycoplasma". (advice from a website re. rat illnesses)