Wasp stings can be life-threatening, as the novelist Susan Hill found. The physical symptoms of her reaction are bad enough. But she is still haunted by the psychological trauma, she tells Caroline Millar
"Nobody quite believes in the middle of being about to die that that is what is going to happen." One hot summer evening, the writer Susan Hill brushed her arm against a dead wasp hidden in the fold of her pillow. Hill is anaphylactic: she has a severe and life-threatening reaction to wasp stings. She felt the sting immediately. But she didn't use the life-saving adrenaline injection she carries in case of such emergencies. She was experiencing denial, a common feature of anaphylaxis. "You just think, 'Oh, it won't really happen'. I don't know why you think this - it is almost a symptom of all sorts of dangerous illnesses."

Hill lives in an isolated Gloucestershire farmhouse, 22 miles from the nearest accident and emergency department. But she didn't want to make a fuss; although she adds, wryly, "I'm not somebody who normally doesn't make a fuss - I tend to make a huge fuss. I'd also tried a treatment at an allergy clinic - being injected with gradually increasing doses of wasp venom. I think I had a feeling that maybe the desensitisation had worked."

Fortunately, she had called her GP, just to be on the safe side. But the delay in administering life-saving treatment reduced her to a parlous state. In the foreword to a new book, she describes what happened next: "My lungs filled with fluid and blood, I spent a terrifying 20-minute ambulance journey close to death and 11 days in hospital." The book Hill is now anxious to publicise is called Life-threatening Allergic Reactions. It covers the psychological as well as the physical features of anaphylaxis, an extreme allergic reaction that has a number of triggers: insect stings are among the most common. While they have not been as well-publicised as the physical effects, states such as denial, extreme anxiety, and post- traumatic shock can haunt the lives of people who suffer from anaphylaxis. Susan Hill has battled against them all.

"When you have nearly died of it there's no point in denying you have the condition any more," she says. "But, even now, when I'm never supposed to go anywhere in the house without shoes on because little beasties do drop off the beams, I still catch myself thinking, 'Oh, I'll just go into the other room.' I desperately try not to do it and I always now do a mental check: 'You won't go into the other room. You will put your shoes on first'. "

From June to October, she stays inside the house most of the time, behind the mesh screens that fit over her windows. She says these restrictions are nothing, just being sensible. Much harder to cope with is the post- traumatic stress she suffered, and still suffers, after her brush with death. "Any huge near-death encounter has got to work its way through your system. You wouldn't be human if you didn't save a huge reaction. You get sudden absolute terrors and dreadful nightmares. The other night I dreamt that Prince Charles was trying to force me to eat a bowl of wasps - I can't think why it was him."

She describes her reactions to seeing a splinter in her hand. Even though she knew it was a splinter and not a wasp sting, she says: "My body went into a huge panic reaction, with breathlessness, pallor, racing heart, faintness, sense of doom, all the symptoms of a real attack."

Eighteen months on, one senses Hilldoesn't like reliving these experiences. But she's also very anxious to tackle ignorance of the condition. "A lot of doctors still don't know as much as they should. The only thing to know is that adrenaline will save your life, and we now have it in a very easily administered form.

"You have to take all the precautions that you know you must take intelligently and meticulously, and not think one day, 'Perhaps it will have got better now'. You must get on with living, knowing that the anaphylaxis is never, ever going to go away."

Anna Williams is a psychologist and one of the book's three co-authors. "It is often easier to deny that you are anaphylactic," she says. "We have so many stresses in our lives that to eliminate one more can seem to be a better thing than facing up to the reality of it, and having to live with that constant cloud of fear over you.

"If you are a summer person and your trigger is wasp stings, it is not particularly nice to know that you have to keep the windows shut, you have to wear something on your feet all the time, you always have to carry an adrenaline syringe. The summer can become a frightening thing."

While researching the book, Williams interviewed a woman who could not face that reality.

"She almost died from her anaphylactic attack, but she still goes around without her medication and her husband goes up the wall at her. This really is serious because if you don't carry medication, waiting 10 minutes for treatment can mean life or death for some people."

By denying their condition, some anaphylactics feel stronger. There is no stigma, no fuss, no need to be constantly checking the surroundings. But it is an illusory strength, bought by repressing fear rather than dealing with them.

It is painful to feel such dread. "I found it very moving listening to Susan Hill," says Anna Williams. "The extreme fear that she felt, and the reactive depression that she suffered afterwards, not withstanding the post-traumatic stress that she had."

The challenge that anaphylactics face is to steer a course between a refusal to face the truth, and a life-inhibiting anxiety. Patients suffering from severe psychological problems can be treated effectively with both drugs, psychotherapy or counselling. And group therapy can foster a sense of taking control of the condition, of gathering courage.

"It is quite frightening if you have had a severe reaction, to accept 'this could happen again, and I could die if it does'," says Anna Williams. "A lot of people get over these things but it does leave a life-long scar".