Why is activated charcoal given to dogs and cats after they’ve eaten something they shouldn’t?

Instructional Guide

Students will learn how to identify signs of chocolate toxicity in dogs. They will explore why veterinarians induce vomiting and feed activated charcoal to sick patients that have ingested chocolate. The lesson will include a short story along with activities that are meant to engage the reader and be helpful learning tools.

Intended Grade Level

This lesson is intended for older elementary students. Students should have a basic understanding of what vomiting is, how food is digested, and how medications can be given.  Students should also have a basic knowledge of the causes and symptoms of abdominal pain. Finally, students should also be aware of what dogs and cats are normally fed (ex. kibble, dog chow, canned cat food, etc.).

Learning objectives

1. Students will be able to explain why dogs and cats should not eat chocolate
2. Students will be able to identify signs of chocolate toxicity in dogs and cats
3. Students will be able to explain why activated charcoal is used to treat chocolate toxicity
4. Students will be able to describe how activated charcoal is fed to sick patients

Lesson Format

1. Students will read the story as a group (10 minutes).
2. Students will work through the learning activities either independently or in small groups (15 minutes).
3. The assessment will focus on writing a short letter in response to a friend who brought their dog to the vet after it was found eating a bag of Hershey kisses. The friend is wondering why their dog came home from the vet clinic with black liquid residue around its mouth (20 minutes).

Lesson Background

Dogs and cats should not eat chocolate because chocolate contains a chemical called theobromine. Interestingly, the more bitter and darker the chocolate is, the more theobromine it contains. Theobromine falls under the class of chemicals known as methylxanthines, which also includes caffeine; this class of chemicals can have effects on the heart and muscles. Since this chemical cannot be processed in a dog or cat in the same way it can be by our bodies, the effects of theobromine can become toxic in pets when chocolate is ingested.

Clinical signs of chocolate toxicity in dogs and cats usually occur within 6-12 hours after ingestion. Sings of toxicity can include nausea, vomiting, diarrhea, lethargy, increased urination, panting, and/or increased breathing rate. More severe signs of chocolate toxicity can include racing heart rate, abnormal heart rhythm, muscle tremors, increased body temperature, seizure, collapse, coma, and death.

When a patient is brought to the vet with signs of chocolate toxicity and a history of chocolate exposure, the vet will begin treatment right away. The vet will first use drugs to induce vomiting and expel as much of the undigested chocolate from the patient’s GI system as possible. The vet may also encourage the patient to eat a slurry of activated charcoal with water and canned food.

Activated charcoal is given to the pet to decrease the absorption of any remaining toxin in the digestive tract. Activated charcoal is made from burnt wood that is activated by the addition of chemicals. Once the charcoal particles become activated, the charcoal is more readily able to bind to bodily toxins, such as methylxanthines. By feeding a slurry of activated charcoal to patients with acute chocolate toxicosis, the activated charcoal will absorb the theobromine and decrease the effects of poisoning. Treatment with activated charcoal can be effective up to four hours after chocolate consumption.

With quick and efficient care, the overall prognosis for a dog or cat is good. At home, pet owners should be sure to store their chocolate in a safe place that is not easily accessible to their pets so that chocolate toxicosis is avoided.

Activities

Students should complete the learning activities after they read the story. Students can work by themselves or in small group (2-3 students).

Common misconceptions and challenge points

Students may be confused as to why chocolate is bad for dogs and cats. Theobromine is a chemical that is toxic to dogs and cats, and since they can’t digest it properly, the build up of theobromine in their systems can lead to clinical signs. Explaining this in terms of food items, such as grass, that other animals can digest but not humans and would result in an upset stomach if consumed in excess might help in explaining this concept.

Getting a dog or cat to eat activated charcoal might be difficult to imagine, but vets take advantage of certain foods that dogs and cats particularly love in order to administer foul-tasting medicines along with them. For instance, dogs tend to really like liquid baby food, peanut butter, and spray cheese, while cats tend to really like Churu and Delectables Squeeze Up treats. Activated charcoal mixed with these treats increases its palatability and eases administration.

Students may also have difficulty understanding the concept of chemical binding. It may be helpful to explain this concept by sticking two things together, such as balls of tape or velcro, that can represent particles of activated charcoal and toxins binding to each other.

Assessment

One of your best friends wrote you a letter this morning. In the letter, your friend wrote:

“Our new dog Daisy is very goofy and she loves treats. She is always sniffing around the house and stealing food off of our plates. This morning, she got into our family’s candy bowl and ate all of the Hershey kisses! She wasn’t acting like her usual self after we found out, and then she started vomiting. Do you think the vomiting was from all the chocolate she ate? My mom drove us to the vet, and the vet told us that chocolate is bad for dogs, but I didn’t believe her. I mean, WE eat chocolate all the time! Why would chocolate be bad for dogs? The vet took Daisy away for a while and then brought her back to us. When Daisy returned, she had all this black goo around her face! What do you think that black goo was, and why would the vet have given it to Daisy anyway? Well whatever it was, she started acting like her goofy self again. Thank goodness!”

For this assignment, please write a response to your friend, addressing the questions:

1. Do you think the vomiting was from all the chocolate she ate?
2. Why would chocolate be bad for dogs?
3. What do you think that black goo was, and why would the vet have given it to Daisy anyway?

Examples of answers to questions:

1. Vomiting is a sign that a dog or cat has just eaten something it shouldn’t, such as chocolate.
2. Chocolate is bad for dogs and cats because they can’t digest it and it makes them ill.
3. The black goo was activated charcoal, and the vet gave it to Daisy to make her stomach feel better.

Further Exploration

For more information on topics covered in this lesson, check out these links:

• Activated Charcoal for Dogs and Cats: https://www.petmd.com/emergency/activated-charcoal-dogs-cats
• 10 Facts About a Dog’s Digestive System: Vet Approved Guide: https://www.dogster.com/dog-health-care/facts-about-dogs-digestive-system
• People Foods Dogs Can and Can’t Eat: https://www.akc.org/expert-advice/nutrition/human-foods-dogs-can-and-cant-eat/