PHILADELPHIA (CBS) – A Philadelphia-based emergency room veterinarian has some advice when it comes to Halloween and your pet.

Seeing strange creatures walk through the front door, Fido may not know it’s Cousin Billy under that furry costume.

Dr. Deborah Mandell, of Ryan Hospital at the University of Pennsylvania‘s school of veterinary medicine (“Penn Vet“), says your pet could get startled and become aggressive — or stressed out.

“So, keep them away from the front door if they get really scared by all the trick-or-treaters, keeping them away from all the noise,” she advises.

Mandell says the biggest problem she sees coming into the emergency room is pets — mostly dogs — who have eaten chocolate.

“All forms of chocolate, in a (great) enough amount, is going to be very toxic.  The plastic and the wrappers from the candy can become a problem and form an obstruction.  And even days later, (pets) can have a problem developing pancreatitis from all the sugar,” she warns.

And if you dress your pet up in a costume, she adds, look out for choking hazards.

And Dr. Mandell is hosting a free lecture on Saturday morning, November 5th, called “First Aid Care For Your Pet.”  Among the topics: pet CPR.

The event, at Penn Vet, 3900 Spruce Street in West Philadelphia, will run from 10am to 11am and is open to the public — but you’ll have to pre-register.  Contact Michelle Brooks at mibrooks@vet.upenn.edu or call 215-898-1480.

This lecture is appropriate for all ages, but participants are asked to not bring their pets.

Reported by John McDevitt, KYW Newsradio 1060