Last updated: September 2026
Quick answer: Never feed chickens avocado skin and pits, dried raw beans, green potatoes, rhubarb leaves, chocolate, caffeine, alcohol, heavily salted food, or anything mouldy. Dried raw beans and mouldy feed are the two that genuinely kill backyard birds most often. Most other scares, including bread, citrus and ripe tomatoes, are overblown.
The never-feed list
Chickens are opportunistic and will try almost anything, which means the responsibility sits entirely with you. These are the foods with a real, documented mechanism of harm.
| Food | Toxic compound | Risk level |
|---|---|---|
| Dried or raw beans | Phytohaemagglutinin | Fatal, fast |
| Mouldy food or feed | Mycotoxins (aflatoxin) | Fatal, cumulative |
| Avocado skin and pit | Persin | High |
| Green potatoes, sprouts, peels | Solanine | High |
| Tomato and potato leaves and stems | Solanine | High |
| Rhubarb leaves | Oxalic acid | High |
| Chocolate and cocoa | Theobromine | High |
| Coffee, tea, energy drinks | Caffeine | High |
| Alcohol | Ethanol | High |
| Very salty food (crisps, cured meat) | Sodium | Moderate to high |
| Onion in large amounts | Thiosulphate | Moderate |
| Apple pips, cherry and peach stones | Amygdalin | Low in practice |
| Anything sprayed with pesticide or weedkiller | Varies | High |
| Raw or spoiled meat | Pathogens | Moderate |
| Sugary processed junk food | None specific | Chronic harm |
Dried beans: the one that actually kills
If you take one thing from this page, take this. Dried and raw beans are the most acutely lethal thing in a normal kitchen for a chicken.
Raw kidney beans in particular contain phytohaemagglutinin, a lectin that destroys red blood cells. A handful can kill a hen within an hour, and there is no treatment once it is absorbed. Red kidney beans are the worst offenders, but all dried beans carry some.
The good news is that heat destroys it completely. Beans that have been properly boiled, or tinned beans, are perfectly safe and are a decent protein source. The danger is exclusively the dry, uncooked bean, which is exactly the form most likely to end up in a scrap bucket or spilled from a bag in the shed.
Mouldy food is the real danger
Mould is the quiet one. It does not drop a bird in an hour like beans do, so people underestimate it, and it kills more backyard chickens than every exotic toxin on this page combined.
Mouldy grain, damp feed, forgotten bread and rotting scraps grow moulds that produce mycotoxins, of which aflatoxin is the most serious. The effects build up: reduced laying, weakened immune response, liver damage, poor growth, then sudden deaths that get blamed on something else entirely.
Three habits handle it. Store feed in sealed metal or heavy plastic bins, not the paper sack. Keep feeders dry and under cover so rain never touches the ration. Clear uneaten wet scraps out of the run the same day, particularly in warm weather.
The Merck Veterinary Manual covers mycotoxicosis in poultry in detail if you want the clinical picture.
Risky in quantity
These are not poisons. They cause problems through dose, habit or displacement.
Salt
Chickens have a low tolerance for sodium compared with mammals. Crisps, salted nuts, cured meats and seasoned leftovers add up quickly, causing excessive thirst, wet droppings and, at high doses, kidney damage. A stray chip will not hurt anyone. A regular habit will.
Onion
Large quantities of raw onion cause haemolytic anaemia through thiosulphate. In practice, chickens rarely eat enough to reach that point, and the more common complaint is that heavy onion or garlic scraps can taint the flavour of eggs. Small amounts in mixed scraps are a non-issue.
Citrus
Not toxic. The old claim that citrus stops hens laying or causes feather-picking has no research behind it. Most chickens simply are not that interested in it. We go through the evidence in can chickens eat oranges.
Raw eggs
Safe nutritionally, but feeding eggs in a recognisable shell form teaches hens that eggs are food, and egg-eating is a habit that is very hard to break. If you feed eggs back, scramble them and crush the shells to powder.
Bread and pasta
Harmless in small amounts, but they are empty calories that displace the balanced ration. A flock filled up on bread is a flock short on protein, and it shows in the feathers and the egg count within weeks.
Foods people wrongly panic about
A lot of the internet advice on this topic is recycled fear. Here is what is actually fine.
| Food | Verdict | Detail |
|---|---|---|
| Ripe tomatoes | Safe | Fruit is fine; leaves and stems are not |
| Bananas | Safe | Peel included if unsprayed |
| Grapes | Safe | Halve them for chicks and bantams |
| Strawberries | Safe | Tops and all |
| Oranges and citrus | Safe | Most hens ignore it anyway |
| Cooked rice | Safe | Uncooked rice is also harmless, despite the myth |
| Cooked beans | Safe | Good protein; only raw beans are dangerous |
| Garlic | Safe | In small amounts; may benefit gut health |
| Cucumber, melon, squash | Safe | Excellent hot-weather treats |
| Cooked meat scraps | Safe | Chickens are omnivores, not vegetarians |
The bigger picture on daily rations, protein levels and life-stage feeds is in our main guide to what chickens eat.
The 90/10 rule
Almost every diet problem in a backyard flock traces back to the same thing: treats crowding out the balanced ration.
At least 90% of what your birds eat should be a complete feed appropriate to their age. Chick starter, grower, then layer. Everything else, scraps, garden produce, mealworms, scratch grain, fits in the remaining 10%.
Two practical points that go with it. First, scratch grain is a treat, not a feed. It is roughly 8% protein against the 16-18% a laying hen needs, and a flock living on scratch will lay badly and molt poorly. Second, any bird eating things other than crumble needs insoluble grit available at all times, because the gizzard cannot grind fibrous food without it.
Calcium is separate again. Offer crushed oyster shell in its own dish rather than mixing it into feed, so non-laying birds, roosters and pullets are not forced to take calcium they cannot use. Excess calcium damages the kidneys of birds that are not laying, which is one of the reasons chicken lifespan varies so much between well-managed and carelessly-fed flocks.
If your chicken ate something toxic
There is no chicken equivalent of activated charcoal you can reasonably keep on hand, and inducing vomiting in a bird is dangerous. What you can do:
- Remove the source immediately and check what the rest of the flock reached.
- Provide clean water with electrolytes. Plain water is second best but still helps.
- Isolate any affected bird somewhere warm, dim and quiet. Stress compounds toxicity.
- Watch for the signs: lethargy, staggering, laboured breathing, diarrhoea, sudden drop in laying, blue or pale comb.
- Call an avian vet if you saw a bird eat dried beans, weedkiller or anything containing chocolate or caffeine. These are the situations where speed matters.
For everything else, most birds that nibble a small amount of something questionable are fine. Chickens are more robust than the internet suggests, and the alarm is usually worse than the outcome.
Frequently asked questions
What foods are toxic to chickens?
Dried raw beans, mouldy food, avocado skin and pits, green potatoes, rhubarb leaves, tomato and potato foliage, chocolate, caffeine, alcohol and anything sprayed with pesticide. Dried beans and mouldy feed are the two that kill backyard birds most often.
Can chickens eat bread?
Yes, in small amounts. Bread is not toxic, but it is empty calories that displace balanced feed. Never feed bread that has started to go mouldy.
Why can chickens not eat avocado?
Avocado contains persin, concentrated in the skin, pit and leaves. The flesh contains far less, but the safest rule is to keep the whole fruit away from your flock.
Are potato peels bad for chickens?
Green peels and sprouts contain solanine and should never be fed. Plain cooked potato without any green tinge is fine in moderation.
Can chickens eat onions?
Small amounts in mixed scraps are harmless. Large quantities of raw onion can cause anaemia, and heavy onion in the diet can taint the flavour of eggs.
Do chickens know not to eat toxic plants?
Not reliably. Free-ranging birds usually avoid the worst plants when they have plenty of other options, but a bored or hungry flock in a bare run will eat things they should not. The ASPCA toxic plant database is a useful check before planting near a run.
How much treat food is too much?
More than 10% of daily intake. Everything above that starts diluting the protein, calcium and vitamin balance of the complete feed.
New to all this? Start with our complete beginner guide to backyard chickens and work out how much space your flock needs before you buy birds.