Adder Bites can occur any time from the end of April onwards. Sometimes you will see your dog leap backwards and catch a glimpse of the snake, sometimes you just become aware of a swelling on the nose, face or feet with a dog which is off colour suddenly. If the bite is on the tongue or lip and enters the bloodstream rapidly then the dog may collapse suddenly because the venom damages the heart or brain. Generally speaking big dogs cope better than small dogs but it does depend on how much venom is injected and where the strike is. Limbs and feet are much safer than noses and lips as the skin is thicker and the blood supply not as good.
If you suspect an adder bite, do not wait around to find some Piriton – if given orally it takes a long time to become absorbed and is unlikely to be strong enough on its own. Transport your dog to your local veterinary surgery as soon as possible to seek expert treatment which may involve administration of antiserum and a stay in a veterinary hospital.