Almost certainly nothing. A neutrino has a roughly one-in-10²² chance of interacting with any given atom. So although trillions pass through you every second, over your entire 80-year lifetime, only about one neutrino on average actually interacts with an atom in your body.
And even that one interaction would be undetectable — the energy released is comparable to a single radioactive decay, which is happening thousands of times per second inside you anyway from natural potassium-40.
The neutrino flux you’re sitting in right now
You are constantly bathed in neutrinos. The main sources:
| Source | Flux at Earth’s surface |
|---|---|
| The Sun | ~6 × 10¹⁰ per cm² per second |
| Cosmic rays via atmosphere | ~10⁻¹ per cm² per second |
| Earth’s interior (uranium, thorium decay) | ~10⁶ per cm² per second |
| Nuclear reactors (if you’re near one) | up to ~10⁹ per cm² per second |
| The cosmic neutrino background from the Big Bang | ~10⁻⁴ per cm² per second (extremely low energy) |
The Sun dominates by far. About 65 billion solar neutrinos cross every square centimetre of your skin every second — day, night, rain, shine. They pass through Earth, through your house, through your bones.
For a typical adult cross-sectional area, that’s roughly $10^{15}$ neutrinos passing through your body per second. Over an 80-year lifetime that’s:
$$80 \times 365 \times 24 \times 3600 \times 10^{15} \approx 2.5 \times 10^{24} \text{ neutrinos}$$
Why almost none of them notice you
Neutrinos interact only via the weak nuclear force, which is incredibly feeble at low energies. The cross section for a typical solar neutrino to interact with an atom is about $10^{-44}$ cm² — twenty orders of magnitude smaller than the atom itself.
To figure out how many interact, multiply the flux × the number of atoms in your body × the cross section:
- Number of atoms in a 70 kg human ≈ $7 \times 10^{27}$
- Solar neutrino flux ≈ $6 \times 10^{10}$ per cm² per second
- Cross section ≈ $10^{-44}$ cm²
The interaction rate works out to about one neutrino per year — and that’s an order-of-magnitude estimate. Some calculations give an interaction roughly once every decade or two.
Over an 80-year lifetime: a handful of interactions, total.
What an interaction would actually look like
If a neutrino does interact with an atom in your body, the most likely process is inverse beta decay or elastic scattering:
$$\bar\nu_e + p \to n + e^+$$
That produces a single positron with about 1 MeV of kinetic energy. The positron quickly annihilates with a nearby electron, producing two 511-keV gamma rays.
The energy released — about 2 MeV total — is similar to a single beta decay of a potassium-40 atom. Your body contains about 17 mg of natural potassium-40 and undergoes roughly 5,000 such beta decays per second. You don’t notice any of them, and you wouldn’t notice the neutrino either.
Could neutrinos ever be dangerous?
In ordinary circumstances, no. The interaction rate is so low and the energy per interaction so small that neutrinos contribute negligibly to your radiation dose.
There’s one theoretical exception: a nearby supernova. A core-collapse supernova within about 10 light-years would deliver enough high-energy neutrinos to cause measurable radiation damage. But the nearest candidate (Betelgeuse, ~640 light-years) is far too far away to be a threat. The natural Earth-side supernova rate at lethal distance is essentially zero.
SN 1987A delivered about $10^{14}$ neutrinos per cm² to Earth — most powerful neutrino event in modern history. The biological dose was negligible because the average human is far away from the source and the cross section is tiny.
A useful sanity check
Neutrinos passing through you per second: ~$10^{15}$. Neutrinos interacting with you per year: ~1. Energy per interaction: ~1 MeV. Energy from interactions per year: ~$10^{-13}$ joules.
For comparison, the dose from background radiation (cosmic rays, soil, internal potassium-40) delivers about $10^{-3}$ joules per year to your body. The neutrino contribution is ten billion times smaller than the natural background you already get and barely notice.
The short answer
Neutrinos pass through your body in unfathomable numbers — about $10^{15}$ per second. Almost none of them interact. Over an 80-year lifetime, only a handful do, each releasing less energy than a single potassium-40 decay. You will never feel a neutrino, and you will never be harmed by one under any realistic circumstances.
For how rare neutrino interactions actually are, see Why are neutrinos so hard to detect?. For where they all come from, see Sources of Neutrinos — Part 1: Solar neutrinos.
Frequently asked
What happens if a neutrino hits you?
Almost certainly nothing. Roughly 65 billion solar neutrinos pass through every square centimetre of your body every second, day and night. The chance that any individual neutrino interacts is so small (about 1 in 10²²) that on average only one neutrino interacts with the atoms in your body over your entire lifetime.
How many neutrinos pass through me per second?
About 65 billion solar neutrinos per square centimetre per second, plus smaller fluxes from cosmic rays, reactors, and geological radioactivity. For a typical adult cross-section, that's something like 10¹⁵ neutrinos passing through your body every second.
Can neutrinos cause cancer or radiation damage?
No. Even if a neutrino did interact with one of your atoms, the energy deposited would be similar to a typical beta-decay electron — much less than the natural background radiation you receive from cosmic rays and potassium-40 in your own body. The interaction rate is also so low that the dose contribution is essentially zero.
Would you feel it if a neutrino interacted in your body?
You wouldn't. The energy involved is comparable to other natural radioactive decays happening inside you all the time. About 5,000 potassium-40 atoms in your body decay every second, each releasing more energy than a typical neutrino interaction would. You feel none of those either.
Cite this article 5 formats
APA
Neutrino Times Editorial Team. (2025, August 22). What happens if a neutrino hits you?. Neutrino Times. https://neutrino-times.com/articles/what-happens-if-a-neutrino-hits-you/
Chicago
Neutrino Times Editorial Team. "What happens if a neutrino hits you?." Neutrino Times, August 22, 2025. https://neutrino-times.com/articles/what-happens-if-a-neutrino-hits-you/.
MLA
Neutrino Times Editorial Team. "What happens if a neutrino hits you?." Neutrino Times, 22 Aug. 2025, https://neutrino-times.com/articles/what-happens-if-a-neutrino-hits-you/.
BibTeX
@misc{neutrino-times-what-happens-if-a-neutrino-hits-you,
author = {Neutrino Times Editorial Team},
title = {What happens if a neutrino hits you?},
howpublished = {Neutrino Times},
year = {2025},
month = {aug},
url = {https://neutrino-times.com/articles/what-happens-if-a-neutrino-hits-you/},
note = {Accessed: 2025-08-22}
} RIS
TY - GEN TI - What happens if a neutrino hits you? AU - Neutrino Times Editorial Team PY - 2025 DA - 2025-08-22 PB - Neutrino Times UR - https://neutrino-times.com/articles/what-happens-if-a-neutrino-hits-you/ ER -