Christmas is associated with an excess of food and top of the list is chocolate. This of course means an increase in cases of accidental ingestion in pets, particularly dogs. We see a huge increase in call numbers relating to chocolate at this time of year – around 20% of all chocolate cases reported to the VPIS occur in December.
The toxic component of chocolate is theobromine, a methylxanthine. It is a metabolite of caffeine (1,3,7-methylxanthine), which is also present in chocolate. The amount of theobromine in products will vary due to natural differences in cocoa beans and the formulation of the products.
The type of chocolate is defined by the quantity (percentage) of cocoa solids and this is defined by law in Europe and the UK.
- White chocolate does not contain any cocoa solids, but it is made primarily of cocoa butter, sugar and milk solids. Theobromine poisoning is not a risk, but the high fat content may present a risk of pancreatitis (24-72 hours after ingestion).
- Milk chocolate contains a minimum of 20% cocoa solids in the UK and a minimum of 25% cocoa solids in the rest of Europe.
- Dark chocolate is made without milk and contains a minimum of 35% cocoa solids.
Signs of chocolate toxicosis include vomiting, diarrhoea, polydipsia, polyuria, restlessness, hyperactivity, tachycardia, hypertension and hyperthermia. Less common effects include haematemesis, haematuria, bloat, tachypnoea, cyanosis and arrhythmias (classically premature ventricular contractions (PVC)). Renal dysfunction may occur but is uncommon.
Treatment is supportive with emesis, repeated doses of activated charcoal, IV fluids and sedation, if required. Although chocolate can make dogs unwell, serious cases are not common, and deaths are rare (typically 1 case per year reported to VPIS and none in recent years). Prognosis is guarded in dogs with seizures or arrhythmias after ingestion of chocolate.