There are several respiratory diseases that can cause nosebleeds in horses. One of these is sinusitis, which causes a red, purulent discharge from one or both nostrils.
One of the main reasons why the skin on horses nose turns red is as a result of inflammation of the skin. This can be due to sunburn or bacterial infection.
So, as we have learned, the reasons why horses fur on nose turning red vary widely, and it is important to have a close look at the nose to see why it is red.