Originally Posted by
Jagboi
Cash is legal, but amounts over 10,000 euro need to be declared to Customs. The dogs smell large amounts of cash to combat money laundering and drug smuggling ( and the proceeds from it)
Or also undeclared business proceeds. If you watch the UK border control TV series, they often have a money sniffing dog at departure with planes to middle east or asia, looking for small shop owners who do mostly cash transaction and not declare all income.