What Causes Frequent Heavy Nose Bleeds In A Child?

My 7 year old son has frequent heavy nose bleeds. We saw a consultant today who was going to spray a numbing spray up his nose and quarterise it there and then but because my son has a cold we have to re attend to have it carried out. I'm worried that the numbing spray may not be enough and that he should have a general anaesthetic. Nothing has been explained to me about this procedure, I feel he wanted a quick in and out. I have been googling this procedure. What do you suggest
Many thanks