Why shells and salt matter more than the nut itself
While pistachio nuts aren't highly toxic to cats, the shells and salt coating create different risks. Those two shells could potentially lodge in your 4kg cat's narrow intestinal tract, especially since feline digestive systems aren't designed to process roughage. The salt may trigger thirst initially, then possibly vomiting as the body tries to expel the excess sodium.
Compare this to your 6kg dog who didn't eat any - their larger size and more robust digestive system would have handled fragments better, but the cat's small body magnifies each risk. Watch for subtle changes like excessive licking of lips (salt reaction) or straining in the litter box (possible obstruction).
Timing matters with foreign objects
Since ingestion occurred just 30 minutes ago, the material is still moving through the stomach. Shell fragments typically cause problems 6-24 hours later when they reach the intestines. Right now, your main focus should be preventing further access and noting the exact time of ingestion for future reference.
Unlike dogs that might chew shells into smaller pieces, cats often swallow fragments whole due to their less thorough chewing habits. This increases the chance of a single larger piece causing a blockage. Remove all pistachios from reach - cats sometimes return to interesting smells.
Multi-pet considerations in small doses
With two pets in the home but only the cat affected, you'll need to monitor asymmetrically. The dog requires no special care at this stage, but be extra vigilant about food left on counters - cats can access spaces dogs can't reach. Pistachio shells on floors pose less risk to your dog's size but remain dangerous for the cat.
Should the cat show signs, you'll need to separate them during recovery to prevent stress-induced symptoms in either animal. Their different metabolisms mean the same quantity affects them differently - what's a mild dose for the dog could be significant for the cat.
What normal looks like for the next day
Expect the cat to drink more water initially due to the salt. Normal bowel movements within 24 hours are a good sign, but inspect the stool for shell fragments. Reduced fecal volume or dry, hard stools suggest the shells may be causing a partial blockage higher up in the digestive tract.
Contrast this with the dog's baseline - their normal appetite and bathroom habits help highlight any changes in the cat. While vomiting once may be salt-related, repeated vomiting or complete food refusal warrants immediate vet attention to check for intestinal irritation from shell fragments.
The full verdict, portion guidance and serving notes are collected on the Pistachios food facts page.