Excerpted from You’re Doing It Wrong.

It’s one of those first aid instructions so widely practiced that it feels officially sanctioned: nosebleed? Tilt your head back. Hold a tissue to your nose. Let the bleeding slow.

Tilt your head back and you’re sending blood down your throat.

Blood that flows backward into the nasopharynx gets swallowed. Swallowed blood irritates the stomach lining and typically causes nausea and vomiting. In a significant bleed, you could swallow enough blood to become nauseated or to make it harder for caregivers to assess how much blood is actually being lost. In rare cases with very heavy bleeding, aspirated blood (entering the airway) creates additional risk.

The correct technique for a nosebleed is the opposite: lean forward slightly, apply firm pinching pressure to the soft part of the nose (not the bony bridge — that accomplishes nothing), and breathe through the mouth. Hold the pressure continuously for ten to fifteen minutes without releasing to check. Most nosebleeds will stop within this time.

Leaning forward keeps blood flowing forward and out of the body, where you can see how much there is, rather than backward into the digestive tract. It also keeps the airway clear.

The American Red Cross, the American Academy of Otolaryngology, and emergency medicine guidelines all recommend the forward-lean, pinch technique. Backward head tilt has been specifically discouraged in medical literature for decades.

The backward tilt persists because it feels intuitively right — holding your head back seems like it would slow blood flow by gravity. But the nose doesn’t drain upward into the skull; it connects backward to the throat. Gravity, in this case, is working against you.