Inhaling or ingesting cat's hairs

Question

I discussed with somebody about the fact that I would like to buy a cat. The answer was that it can be dangerous, but in a different way than I expected.

Their argument was that inhaling or ingesting the cat's hairs can cause the (human) body to react, causing local bleeding, complications, possibly encouraging cancer growth. Also, their statement was that the human body does not have the ability to remove those hairs - similar to a cat vomiting hair balls.

While it makes sense in a way, it is still contrary to the overwhelming experience: people own cats and do not get sick - at least, not in this way.

Does anyone have reliable information about this?

Answer 1

That sounds like made up panic. Now, I will freely admit this anecdotal, but having grown around cats, with several friends who also grew up with cats, this "ingesting cats hair is dangerous" doesn't really hold water. It is about as likely as ingesting your own hair, and about as dangerous.

Now, matter is different if you have allergies, in which case it doesn't really matter. Although I would share anecdote of my brother, who does have pet allergies, but they work rather interestingly. Without a cat or other pet, his body becomes sensitive and will react to various animals, but if he has pets or regularly interacts with animals, his body "gets used to it" (highly scientific term used by doctor) and stops overreacting.

In order to have enough hair (human or cat. Human body treats two as the same, hence my "as dangerous" comment earlier) to cause trouble you need to be actively eating it. I do not mean "swallows one strand every week", I mean actively picking it up and eating clumps of them.

TL;DR

No, it is not dangerous unless you are actively trying to eat as much at hair as possible.

Answer 2

Your friend probably either was the victim of a scam or heard of an anecdotal story and misunderstood.

Regular cell damage due to bruising, local bleeding and other processes like inflammation can sometimes lead to cancer if the irritation is chronic. There are also a few viruses (like HPV) that can lead to changes in cell structure and eventually cancer.

Now, how would cat hair cause such a chronic irritation? My honest oppinion is that it can't. The usual hairs in a cat's coat are about as thick as human hair and our bodies are well equiped to deal with those if not ingested in vast amounts.

Whiskers are much thicker, though, and the scaly outer structure gives them interesting physical properties. If you let a hair glide through two of your fingers, you'll notice that it glides very smoothly from root to tip, but with much more resistance from tip to root (the same applies to human hair, but to a lesser extent). This means that if you ingest a piece of whisker, if it survives all the way into the intestine and if it happens to get caught root first in your intestine (or you manage to poke it into your skin somehow), it can only move in one direction. It migrates very slowly through the tissue, causing constant irritation and microscoping tissue damage, and the body will eventually encapsulate it in a dense ball of cells (commonly known as "tumor") as a protective measure. This process is known from awns or "mean seeds" (the tough hairs at the tips of grass seeds) as documented here.

To be honest, I have no idea if this can actually happen with hairs. The human body is able to digest hairs in the stomach and might be able to desintegrate cat hairs outside of the digestive system. But I couldn't find any evidence that any human ever developed cancer due to cat hair.