Conkers can killConkers, these shiny brown "nuts" - the seeds of the horse chestnut tree - are poisonous to dogs. If chewed and swallowed, conkers are highly toxic, and swallowing them whole can cause intestinal blockages.
Horse chestnut (Aesculus hippocastanum)
Lucky, a three-year-old Staffordshire Bull Terrier was rushed to The Blue Cross animal hospital in Victoria, London, by his anxious owner, after he'd been extremely sick and refused to eat or drink. Vets discovered that Lucky had a conker blocking his intestines and a quantity of chewed-up conkers in his stomach, which had poisoned him. Lucky needed emergency surgery and was monitored in the clinic by vets for several days to make sure the poisoning wasn't fatal.
Earlier that day Lucky had been playing with a group of youngsters in south London. They had no idea that encouraging Lucky to play with, chew and catch conkers could be so dangerous to him.
Warning in Dogs Monthly, November 2011