Eating a horsehair worm is generally not dangerous for humans and does not result in an actual infection, though it might cause brief stomach discomfort or vomiting in some cases.

What horsehair worms are

Horsehair worms (phylum Nematomorpha) are long, very thin parasitic worms that naturally infect insects and other invertebrates like crickets, grasshoppers, and beetles. As adults they live in water and do not feed; their digestive system is essentially nonfunctional, and their life stage is focused on reproduction.

Can they infect people?

  • Horsehair worms are considered harmless to humans and other vertebrates because they do not parasitize mammals, birds, reptiles, or fish.
  • Scientific reviews and case reports describe them in people as “pseudoparasites,” meaning they may be encountered (for example, in vomit, urine, or stool) but do not actually invade or live in human tissues.

What happens if you eat one?

If someone accidentally swallows a horsehair worm in water or in an infected insect, a few things are possible:

  • The worm may irritate the stomach or intestines briefly, causing mild abdominal discomfort or vomiting, and then be expelled.
  • The worm’s tough outer cuticle can let it pass through the digestive tract intact and be seen later in stool, but this still does not mean it has infected the body.
  • Extension and pest-management sources state that infection “never occurs” in humans; at most, there may be mild, short-lived intestinal upset.

When to see a doctor

Even though horsehair worms themselves are not known to harm humans, it is still wise to seek medical advice if:

  • You have persistent or severe abdominal pain, vomiting, fever, or general illness after eating contaminated food or water.
  • You find a worm in vomit, stool, or urine and are unsure what it is; a doctor or laboratory can help identify it, since other parasites (unlike horsehair worms) can cause real disease.

Forum and “latest news” context

Online forums sometimes include distressing stories from people who believe they have ongoing infestations with horsehair worms, often describing skin or systemic symptoms. Medical and parasitology literature, however, does not support horsehair worms as true human parasites and instead emphasizes that they pose no recognized public health risk.

TL;DR: In normal circumstances, nothing serious happens if you eat a horsehair worm: it cannot set up an infection in your body and may only cause brief digestive discomfort before being expelled.

Information gathered from public forums or data available on the internet and portrayed here.