What the most danger cause for tiny amount of nose bleeds in both nostrils when blowing nose, in 40 years old women?

Atrophic rhinitis: Assuming that you are not using nasal steroid aimed at the center of the nose , Afrin -like nasal spray, or cocaine. the most likely cause is dryness . You may try a nasagel spray to keep the nose moist especially on dry and windy days. If problem persists, consult ENTor allergist to check for allergies, sinusitis etc. I also assume that you have no unusual amount of bruising.