Most dog owners know chocolate is off the table. Fewer know that the base of nearly every Indian meal, the onion-garlic tadka that goes into dal, sabzi, biryani, and curry, sits in the same category of genuine toxins for dogs. The risk is not about flavour or digestion. It is about what specific compounds in these ingredients do to a dog's red blood cells, and why cooking does not make them safe.
The compound that causes the damage
Onions, garlic, leeks, and chives all belong to the Allium family. Every member of this family contains organosulphur compounds, in garlic, the most active form is allicin and its breakdown products; in onion, the primary culprits are n-propyl disulphide and related thiosulphates. When a dog eats any part of these plants, the compounds are absorbed into the bloodstream and attach to haemoglobin, the protein inside red blood cells that carries oxygen. Once attached, they cause oxidative damage to the cell membrane. The body reads these damaged cells as foreign and destroys them. The result is haemolytic anaemia: a drop in red blood cells that can happen gradually over several days, which is part of why owners often do not connect the curry from Tuesday with the sick dog on Friday.
Why cooked onion and garlic are just as dangerous
A common assumption is that cooking breaks down the toxin. It does not. Organosulphur compounds survive heat. The onion that caramelised in the pan for twenty minutes, the garlic that fried in oil until golden, the paste that slow-cooked in a gravy for an hour, all of them retain enough of the compound to cause harm. Dried and powdered forms are actually more concentrated by weight than fresh, which matters because garlic powder and onion powder appear in some commercial seasonings and snack foods. The toxic dose for dogs is low: garlic is considered roughly five times more potent than onion by weight. Even a small amount of either, given regularly in table scraps, can accumulate enough oxidative stress to push a dog into clinical anaemia.
What the threshold actually looks like in practice
Toxicity studies in dogs place the threshold for onion at roughly 0.5 percent of body weight, meaning a five-kilogram dog could be affected by as little as 25 grams of onion. That is less than a quarter of a medium onion, or a few spoonfuls of cooked curry. For garlic, the threshold is lower still. These are not dramatic quantities. A dog that cleans a plate of dal or gets a piece of roti soaked in curry gravy is not eating a negligible amount by these measures. The risk compounds with repeated exposure: a dog fed table scraps daily does not need a single large dose to develop anaemia.
Signs that something is wrong
Haemolytic anaemia does not look like a sudden poisoning. The signs build over two to five days after exposure and are easy to miss or attribute to something else. Watch for pale or yellowish gums, press a finger to the gum, release, and the colour should return within two seconds; sluggishness and a reluctance to move that is out of character; rapid breathing or an elevated heart rate at rest; reduced appetite; and urine that looks darker or more orange-red than usual, which can indicate the presence of haemoglobin from lysed cells. If a dog has eaten a significant amount of onion or garlic and you are not yet seeing signs, that window is not reassurance, it is the delay before the damage shows. A dog showing pale gums, rapid breathing, or obvious weakness after any known or suspected Allium exposure needs a vet the same day, not a wait-and-see approach.
What to do if your dog ate curry or a garlic-heavy food
If the exposure was in the last one to two hours and the amount was meaningful, a vet can consider inducing vomiting, but this is a clinical decision, not a home step. Do not attempt to induce vomiting at home without veterinary guidance. If the dog is already showing signs of anaemia, the priority is supportive care, which in serious cases can include a blood transfusion. At home, the practical answer is prevention: keep curry, dal, biryani, and any cooked food that contains onion or garlic out of reach and off the plate. Roti on its own is not a problem; roti torn off and dipped in sabzi or gravy is. The distinction is worth making clearly in a household where everyone feeds the dog.