Why is it risky?
Aluminum foil is not chemically toxic, but used foil often carries residues of food (meat, fish, butter) that attract cats to lick and chew on it. Ingested foil pieces have sharp edges that can lacerate oral tissue, the esophagus, or the intestinal wall. Obstruction is also possible with larger pieces.
Affected Systems
Digestive
Symptoms
None if not ingested. If ingested: vomiting (possibly with blood from lacerations), reluctance to eat, lethargy, abdominal pain, potential obstruction signs.
What To Do
Dispose of foil immediately after use, in a closed bin. If ingested: contact vet for advice based on size of piece and symptoms.
Notes
Aluminum foil is often suggested as a deterrent, many cats dislike walking on it. This use is reasonable, but foil should never be left accessible as a play item, as cats may chew and ingest it. Foil placed under food bowls or on furniture surfaces as a deterrent is generally safe.
Sources
→ ASPCA Animal Poison Control Center — aspca.org
→ VCA Animal Hospitals — vcahospitals.com