Why does your gerbil have a bloody nose?

Gerbils mucas is red. People often mistake it for blood. Chances are the gerbil's nose is just irritated, but if it is prolonged it could be caused by an allergy from the bedding or nesting materials used. If this is so switch beddings and see what works. Also make sure all nesting material is unfragranced or dyes because they are known to irritate gerbils.