The woman told police she was walking her dog near downtown Des Plaines Tuesday when she found a hot dog with a bluish-green tint in it. She took it to her vet, who told her it was rat poisoning.
Mel Dziedzic, who works at Riser Animal Hospital in Skokie, posted a photo of the hot dogs on Facebook to warn others about the incident.
It's not clear how long the hot dogs had been there or who had put them there.
Police said there have been no reports of any sick pets.