PEOPLE taking their dog for a walk on a common near York are being warned about the presence of numerous adders.

James Howard tweeted that he saw 20 of the snakes in the heather when he was on Strensall Common yesterday.

He said: "A warning for everyone walking their pets. It's that time of year again when the young adders start coming out for a wander."

Adders are the UK's only venomous snakes.

The NHS's advice if you are bitten by one is to call 999 or go to A&E immediately.

It says that while you're waiting for help, you should stay calm, keep the part of your body that was bitten as still as you can, lie in the recovery position if you can, take paracetamol for any pain, try to remember the colour and pattern of the snake to tell the doctor and take off any jewellery and loosen clothes near the bite, in case it swells.

It says you should not go near the snake, or try to catch or kill it, try to suck or cut the poison (venom) out of the bite, tie anything tightly round the part of the body where the bite is or take aspirin or ibuprofen, as they can make bleeding worse.