Chocolate (theobromine): toxic for dogs

Why is chocolate dangerous for dogs?

Chocolate contains two methylxanthines: theobromine and caffeine. Both block adenosine receptors in the body, leading to stimulation of the central nervous system, increased heart rate, increased urine production and increased muscle tension [3][4].

The crucial problem is that dogs break down theobromine much more slowly than humans. The half-life is approximately 18 hours, meaning the substance remains active for a long time and symptoms in cases of severe poisoning can persist for up to 72 hours [4].

Not all chocolate is equally dangerous

The theobromine content varies greatly depending on the type of chocolate:

This means that a small amount of dark chocolate can already be dangerous for a small dog, whereas white chocolate poses significantly less risk for this reason — although white chocolate can also contain other harmful ingredients [3][4].

Course of poisoning

Initial symptoms usually appear 6 to 12 hours after ingestion. The higher the amount of theobromine per kilogram of body weight, the more severe the consequences [1][4]:

• Mild poisoning — vomiting, diarrhoea, excessive thirst and restlessness
• Moderate poisoning — severe restlessness, muscle tremors, increased heart rate
• Severe poisoning — epileptic seizures, cardiac arrhythmias, coma

Small dogs run a much greater risk than large dogs from the same amount of chocolate, simply because the theobromine intake per kilogram of body weight is higher.

Seasonal risk

Epidemiological research in the United Kingdom showed that exposure to chocolate occurs significantly more often around Christmas (OR 4.74) and Easter (OR 1.97) [2]. This is related to larger stocks of chocolate in the home and gift packages that are accessible to dogs. Extra vigilance during holidays is therefore additionally justified.

What to do in case of (suspected) ingestion

Do not wait and see. Contact a veterinary surgeon or an animal poison control centre immediately, even if the dog is not yet showing symptoms.

• Within 2 hours of ingestion, inducing vomiting is most effective — but do this only under the supervision of a veterinary surgeon, never on your own initiative [4].
• The veterinary surgeon can then administer activated charcoal to slow further absorption.
• In severe cases, intravenous fluids, sedatives for tremors and anti-arrhythmic drugs are required — this always requires veterinary care [1][4].

Do not wait for symptoms to decide to call the veterinary surgeon. When making contact by telephone, provide the following as accurately as possible: the dog's weight, the type of chocolate and the estimated amount. This information helps the veterinary surgeon quickly determine how urgent the situation is.

'Natural' does not mean safe

Chocolate is a natural product, but that does not make it any less dangerous for dogs. Theobromine is a plant substance with a demonstrably toxic effect in dogs — the distinction between 'natural' and 'safe' is vital here [3].