New divers frequently report nosebleeds after diving primarily because they are unaware of the importance of equalizing the sinuses and middle ears (via the Valsalva method). The barotrauma that is produced when the sinuses are not cleared can cause blood vessels in the lining of the nose to burst. These vessels lie very close to the top of the mucous membrane lining in the nose and sinuses, and the blood can come from the lining in either. This type of barotrauma, generally the result of air being trapped within the sinuses, is not always painful, though the presence of blood can be disconcerting to a new diver. With this type of injury, blood can run down the back of the throat or pool in the sinus below the eye and emerge at a different time. It can also act as a growth medium for bacteria and result in sinus infections.
Individuals with a history of sinus trouble, allergies, a broken nose, or deviated septum, as well as divers who currently have colds may find the clearing procedure difficult to accomplish and may experience a problem with nosebleeds. It's always best not to dive with a cold or any condition that may block the sinus air passages.
We suggest a slow, gentle descent with frequent equalizing to help decrease the risk of sinus barotrauma. Divers who are unable to clear their sinuses or have frequent nosebleeds when scuba diving should see their personal physicians or ear-nose-and-throat specialists for evaluation.