What are the effects of swallowing own blood from nosebleeds?

Question

I've seen people on the internet claim that you shouldn't tilt back your head during nosebleeds, because blood could get into your lungs or stomach. When I asked people I know what they do during nosebleeds and what they know, most of them tilt their heads back and put cotton tampons or handkerchiefs in the nostrils. None of them have suffered any trauma caused by swallowing blood, and as far as I know, it's rare for seriously bad effects to occur like this.

There is an infamous photo of a very large branching blood clot (http://www.snopes.com/photos/medical/bloodclot.asp) which is used to scare kids about nosebleeds, but it seems to be an exceptionally rare occurrence. At least that's so uncommon that I've only seen that in this one picture.

One common thought that goes through minds of people I've talked to seems to be "Blood loss is a thing, and I'm losing blood, so I better swallow it back into myself".

I'd like to ask the more knowledgeable folk on this site: Is swallowing own blood from nosebleeds harmful, neutral or beneficial?

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I've found a question on SE about consuming blood in general, and the recommendation is against that, but in that case it's extra blood that wasn't in your own body's circulation. So this is a different question, just in case.

Answer 1

Blood irritates the stomach and in sufficient quantity will cause nausea and vomiting, so that would make it harmful.

https://www.emedicinehealth.com/stopping_a_nosebleed-health/article_em.htm

Do not tilt your head back. This may cause blood to run down the back of your throat, and you may swallow it. Swallowed blood can irritate your stomach and cause vomiting. And vomiting may make the bleeding worse or cause it to start again. Spit out any blood that gathers in your mouth and throat rather than swallowing it.

The story behind the photo you posted may or may not be accurate, but clearly the patient in question was not well. Blood running down the trachea of a healthy, alert person would trigger an immediate cough reflex.