Why size doesn't change safety for cats
Your 4 kg cat's small stature makes her vulnerable to many toxins, but sesame seeds aren't one of them. Unlike lilies or chocolate, which are dangerous in tiny doses for cats, plain sesame seeds contain no feline-specific toxins. A teaspoon is about 3 grams—less than 1% of her body weight. For perspective, that's like a 150 lb human eating a small handful; noticeable but not hazardous. Her digestive tract will treat them as inert fiber.
Cats process plant matter differently than dogs, but this amount is trivial. Expect to see whole seeds in her litter box within 24 hours, possibly mixed with slightly looser stool. This isn't true diarrhea unless it's watery or frequent. The oil in the seeds might give her stool a glossier appearance temporarily. Unlike dogs, cats rarely overindulge in strange foods, so one teaspoon is likely all she took—making the dose even less concerning.
The real risks for a curious cat
While the seeds themselves are safe, consider how she accessed them. If they were on a plate with garlic-seasoned food or mixed with raisins, those accompanying foods could be toxic. Plain sesame seeds are harmless, but cats often swipe food from dangerous contexts. Check the area for spilled alcohol, onion powder, or other feline hazards that might have hitchhiked with the seeds.
Also watch for non-digestive signs. Cats stress more easily than dogs, and the commotion of being caught stealing food might upset her more than the seeds themselves. If she hides or skips a meal, it's likely behavioral, not physical. Offer fresh water and her regular food as usual. Unlike dogs, cats rarely vomit from minor dietary changes unless they have a pre-existing condition, which isn't mentioned here.
Why you won't see typical 'toxic' symptoms
With truly dangerous foods, cats show specific warning signs like dilated pupils, ataxia, or rapid breathing within hours. Sesame seeds cause none of these because they lack theobromine, allicin, or other feline toxins. At most, your cat might have one slightly soft stool from the extra fiber—not the repeated vomiting or lethargy that signal poisoning. Her small size means you'd see symptoms quickly if they were coming; silence is reassurance.
Focus on litter box monitoring rather than physical exams. Healthy cats are fastidious about grooming, so if she's licking her lips excessively or pawing at her mouth, it's worth a vet call—but this would suggest a spice or cleaning product residue, not the seeds themselves. Since you saw her eat plain seeds, these signs are unlikely. More probable is complete indifference, as cats often ignore minor stomach upsets that would concern dogs.
When feline habits override food fears
Cats self-regulate intake better than dogs, which works in your favor here. Unlike a dog that might gorge on a whole bag of seeds, your cat likely took one exploratory taste. Her natural caution with new foods means the teaspoon you saw is probably the full dose. This makes the risk even lower than for a dog of the same size, who might actively seek more.
Use this as a chance to cat-proof your table settings. While sesame seeds are safe, many human foods aren't. Her successful theft proves she can access the table, so consider moving tempting items farther back. For now, though, relax. A 4 kg cat can handle this tiny plant-based snack with no more drama than a slightly different litter box deposit tomorrow. No vet visit needed unless she shows signs completely unrelated to sesame seeds, like coughing or collapse.
The full verdict, portion guidance and serving notes are collected on the Sesame seeds food facts page.