Bleeding from nostril

[mtnridr@pacbell.net]

Hi, everyone...

Wondering about my husband's 12-year-old gelding, who has 
recently started bleeding out of one nostril again.  He did this 
some time ago, and vet said probably allergy--only one nostril, 
thin blood (sometimes scant trace).  We went out for an hour today, 
and it happened again (2x in a month).  Anyone have any horses who 
do this on the trail?

Thanks for any assistance...

Chris