Dogs metabolise theobromine roughly six times slower than humans - their half-life is 17.5 hours compared to our 2-3 hours. This means the toxic compound accumulates in their system rather than being cleared out quickly. What starts as 'ate a chocolate bar' can become 'life-threatening poisoning' within hours because the dose keeps building whilst their body struggles to process it.

Theobromine attacks on three fronts. First, it overstimulates the cardiovascular system, causing rapid heartbeat, arrhythmias, and potentially cardiac arrest. Second, it triggers the central nervous system, leading to hyperactivity, tremors, and seizures. Third, it irritates the gastrointestinal tract, causing vomiting and diarrhoea. The combination is particularly nasty because by the time symptoms appear (usually 2-4 hours), there's already enough theobromine in their bloodstream to cause serious harm.

Emergency vets dread Christmas and Easter. A 10kg dog (think Jack Russell) eating just 15g of dark chocolate - about three squares - needs immediate veterinary attention. The average Cadbury's Dairy Milk bar is 45g, which would be severe poisoning for a small dog and dangerous for a medium one. The real problem is that dogs can smell chocolate from across a room but mysteriously lose all recall training when they find an unattended Easter egg.