During the week of Halloween last year, calls to Pet Poison Helpline concerning dogs that ingested chocolate increased by 209% over a typical week at the animal poison control center. Despite increased awareness over the past few years, chocolate poisoning continues to pose a serious danger to dogs, especially at Halloween.

During the week of Halloween, our total call volume increases by about 12 percent, and the majority of those calls involve dogs that ate chocolate," said Justine Lee, DVM, DACVECC and associate director of veterinary services for Pet Poison Helpline.

One such dog was Thor, an 8 month old Great Dane puppy. While his owner was away, he ingested four entire two-and-a-half pound bags of Halloween candy, most of which contained milk chocolate. Upon finding the empty candy bags and a very sick 95-pound puppy, Thor's owner immediately called Pet Poison Helpline. Thankfully, Thor's stomach was so upset from ingesting nearly 10 pounds of chocolate candies, he vomited on his own. According to his owner, "What he left behind was about the size of an over-filled dinner plate." Thankfully after carefully monitoring his condition with Pet Poison Helpline, it was determined that Thor didn't need to be hospitalized.

Of all candy, chocolate is most poisonous to dogs. Many dogs are inherently attracted to the smell and taste of chocolate, making it a significant threat. In general, the darker and more bitter the chocolate, the more poisonous it is. The chemicals in chocolate that are dangerous - methylxanthines - are similar to caffeine and more heavily concentrated in the darker varieties. In fact, just 2-3 ounces of Baker's chocolate can make a 50-pound dog very sick. Milk chocolate, on the other hand, is less dangerous. It can take up to a pound of milk chocolate to cause poisoning in that same 50-pound dog. White chocolate rarely causes true chocolate poisoning because it contains very low amounts of methylxanthines; however the high fat content may result in pancreatitis (see Candy Overindulgence below).

Pet Poison Helpline recently produced a video with information about chocolate poisoning titled  Kitchen Dangers, available online.

If you think your dog may have ingested chocolate, call your veterinarian or the Pet Poison Helpline right away for medical assistance. Untreated, chocolate poisoning in dogs can result in vomiting, diarrhea, lethargy, agitation, increased thirst, an elevated heart rate, or seizures.

Other Halloween food-related hazards for pets are candy wrappers, raisins and general candy overindulgence.

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• Candy wrappers - When pets eat candy, sometimes they eat the wrappers too. Ingestion of foil and cellophane wrappers can cause a life-threatening bowel obstruction, which can require surgical intervention. Watch for vomiting, decreased appetite, not defecating, straining to defecate, or lethargy. X-rays may be necessary to diagnose this problem.

• Raisins - Instead of candy, some health-minded households distribute mini-boxes of raisins. Very small amounts of raisins are poisonous to dogs (as well as grapes or currants) and can cause kidney failure. Any ingestion of raisins or grapes should be treated as potentially toxic and necessitates a call to Pet Poison Helpline or your veterinarian. As the poison in raisins is more concentrated as compared to grapes, only a small amount of raisins can result in signs of vomiting, nausea, decreased appetite, lethargy, abdominal pain, and severe kidney failure. Raisins should be stored in secure containers far from their reach.

• Candy overindulgence - Pets are indiscriminate when it comes to eating can easily gorge themselves. Large ingestions of sugary, high-fat candy can lead to pancreatitis. Potentially fatal, pancreatitis is inflammation of the pancreas and very painful. It may not show up for one to four days after the pet ingests the candy. Signs include decreased appetite, vomiting, diarrhea, lethargy, abdominal pain, and potentially, kidney failure or organ damage.

Halloween glow sticks, glow jewelry and costumes can also be dangerous. Every year, the Pet Poison Helpline receives numerous calls concerning cats that have punctured and chewed on glow sticks and glow jewelry. While not usually life-threatening, they can cause mouth pain and irritation, as well as profuse drooling and foaming at the mouth. If you dress your dog or cat in a costume, be sure it doesn't impair his vision, movement or air intake. If the costume has metallic beads, snaps or other small pieces, be aware that some metals (especially zinc and lead) can result in serious poisoning if ingested.

This Halloween season, help keep your dogs and cats safe and keep chocolate and other holiday fare out of their reach. If you think your pet has ingested something poisonous, it is always better (and less expensive) to get help immediately. Contact your veterinarian or the Pet Poison Helpline at 1-800-213-6680 for life-saving help.

Lorie Huston has been practicing veterinary medicine for over 20 years. Besides a successful career in a busy small animal hospital in Providence, RI, Lorie is also a successful freelance writer specializing in pet care and pet health topics. Currently, she is the feature writer for the Pet Care section at Suite101.com, a contributing writer for Veterinary Medicine at About.com and the  National Pet Health Examiner at Examiner.com. Lorie also publishes her own blog, The Pet Health Care Gazette and manages an increasingly popular facebook page, The Voice of Pet Care.  

The Pet Poison Helpline is a service available 24 hours, seven days a week for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. Staff can provide treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline's fee of $35 per incident includes follow-up consultation for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at the Pet Poison Helpline.