While parental fears about razorblade-ridden chocolate and poisoned candy apples have mostly subsided in recent years, pet owners should still be concerned on Halloween. That’s because there are plenty of ways for pets to find trouble—particularly if left alone with a bag full of goodies.

Here are the biggest Halloween pet hazards to watch out for, courtesy of Pet Poison Helpline. Pass on the information to your clients, and you might just avoid any Halloween-related emergencies this year.

Chocolate

Why it’s dangerous: Chocolate is more poisonous to pets than any other candy. Chocolate contains methylxanthines, chemicals similar to caffeine that can quickly sicken dogs. In general, the darker the chocolate, the more poisonous it is.

What to watch for: Symptoms in dogs that have ingested chocolate include vomiting, diarrhea, lethargy or agitation, increased thirst, an elevated heart rate, and, in severe cases, seizures.

Candy

Why it’s dangerous: It’s hard enough for a human to stop at just one piece of candy, so imagine how difficult it is for a pet. Large ingestions of sugary, high-fat candy can lead to pancreatitis, which may not show up for two to four days after the pet ingests the candy.

What to watch for: Pets that have ingested candy may show signs such as decreased appetite, vomiting, diarrhea, lethargy, abdominal pain, and even kidney failure or organ damage.

Candy wrappers

Why they’re dangerous: The candy itself isn’t the only threat. Ingestion of foil and cellophane wrappers can cause life-threatening bowel obstructions, which often require surgical intervention.

What to watch for: Symptoms in pets that have ingested candy wrappers include vomiting, decreased appetite, not defecating, straining to defecate, or lethargy.

Raisins

Why they’re dangerous: While good-intentioned neighbors may hand out raisins as a healthy alternative to candy, very small amounts of raisins (or grapes) can cause kidney failure in dogs and cats. Some dogs develop idiosyncratic reactions at any dose—in other words, ingesting any amount can cause serious damage.

What to watch for: Pets that have ingested raisins may show signs like vomiting, nausea, decreased appetite, abdominal pain, and severe kidney failure.

Glow sticks and jewelry

Why they’re dangerous: Pets love to chew on things they’re not supposed to, and cats in particular seem to love these items. Over the past year, 70 percent of Pet Poison Hotline’s calls relating to glow sticks and jewelry involved cats. In addition to the choking hazard, the contents of glow sticks can cause pain and irritation in the mouth.

What to watch for: Keep an eye out for mouth pain, as well as profuse drooling and foaming at the mouth.

Costumes

Why they’re dangerous: Your clients may love the costume, but does their pet? Some costumes can cause discomfort in pets, and any metallic beads, snaps, or other small pieces (particularly those made of zinc or lead) can result in serious poisoning if ingested. Finally, don’t ever dye or apply coloring to a pet’s fur, even if the dye is labeled non-toxic to humans.

What to watch for: If clients dress their pets in costumes, teach them to make sure it doesn’t impair the pets’ vision, movement, or air intake.