What would cause nose bleeds in a 2 year old?

Usually irritants : Nose bleeds in toddlers are usually a reflection of nasal irritant effect. Dry heat, smoke, dust, fumes all lead to irritation and occasionally infection.This causes small nasal capillaries to bleed, often as the face is rubbed into bed linen in sleep. Removing as many irritants from their life as possible can help as can nasal saline wash, nasal saline gel reasonable humidity within the home.