Most stings are painful but harmless, and only affect the area around the sting. However, some people can have an immediate and more widespread allergic reaction to being stung such as swelling or itching away from the site of the sting or anaphylactic shock, which can be fatal. Anaphylactic shock is quite rare, affecting approximately 3 people in 100, and it normally only happens with a wasp sting.
If collapse follows being stung or if you have wheezing or difficulty swallowing, you should call 999 immediately for an ambulance. You might be having an allergic reaction and may need to have an adrenaline injection, antihistamines, oxygen and/or an intravenous drip. Similarly, stings near the eye or inside the mouth should receive immediate medical attention.
Remember bee stings are to a great extent ignored by beekeepers in their thousands throughout the world, since they suffer no ill effects from them. They are even reputed to be good for rheumatism! More advice on stings can be found at the following links to Anaphylaxis or Allergies