Ms Reading died from a severe allergic reaction to peanuts - a condition that has resulted in at least eight deaths in Britain in the past two years and - according to Nicholas Soames, the Minister for Food - threatens as many as 5,000 people. The numbers at risk are increasing rapidly: in his May newsletter to GPs, the Chief Medical Officer will include guidance about how to spot and treat the allergy.
Ms Reading had not eaten a packet of peanuts - she knew that she suffered from the allergy. Her parents were at first baffled as to what caused her death. Then they found a till receipt in her handbag, showing that she had bought a slice of lemon meringue pie in a restaurant in Debenhams. The coroner later established that the pie was finely sprinkled with peanuts.
This is what is so alarming about the allergy. One woman died after eating a cake containing peanuts; another after eating a pretzel containing peanut butter.
Allergic reactions can be set off simply by peanut protein - in some cases, entering a room where a peanut smell lingers can be enough to make people feel ill.
'It is quite obvious what a peanut is; it is not obvious where you get peanut oil,' says Dr Harry Amos, director of medical affairs at Peptide Therapeutics, which is trying to develop a vaccine to block a variety of allergic reactions. 'It is almost impossible to avoid peanuts.'
According to one leading consultant allergist, three out of the seven leading milk brands use peanut oil in their preparations. This, he believes, leads to allergy-prone babies reacting adversely to peanut substances from a very early age; and that is why the incidence of peanut allergy is increasing so rapidly.
Peanut oils are used as flavour- carriers in ice-cream, cereals, snacks, soups, stocks, cakes, biscuits and desserts. All the recorded deaths, however, were the result of eating whole or crushed peanuts. The victims suffered from an anaphylactic (whole- body allergic) reaction. It involves blood vessels leaking, bronchial tissues swelling, the face and lips puffing up, falling blood pressure, choking and eventual collapse. Some children's heads swell up to resemble miniature versions of the Elephant Man.
The adverse reaction can only be reversed by inhaling - or, for severe shock cases, injecting - adrenalin. Some allergists think that many anaphylactic deaths go unrecorded: they are put down to heart failure, asthma or infant death syndrome.
David Reading, Sarah's father, formed the Anaphylaxis Campaign after her death. He wants better food-labelling to warn potential victims.
First, he says, manufacturers are not obliged to say that a product contains peanut oil specifically, only that it contains vegetable oil. Secondly, they are not obliged to spell out the ingredients of anything - a sauce, for example - comprising less than 25 per cent of the dish.
Mr Reading also wants to warn allergic people of the potential dangers. He knew that his daughter was allergic to peanuts and nuts but thought that the worst she risked was a skin rash. 'It was a complete and utter shock that anything like that could be so devastating.'
It is estimated that about 2 per cent of the population suffer from food allergies. Of these, many do not have life-threatening reactions. But, in the worst cases, the condition requires constant vigilance. Claire, the 15-year-old daughter of Geraldine Evans, from Clanfield, near Portsmouth, Hampshire, carries an adrenalin injector at all times and wears a medical-alert tag on a chain. 'If she were ever to eat a peanut it would kill her,' Mrs Evans says.
Food labels, Mrs Evans says, will often not tell you whether a manufacturer has used peanut oil or an essence of peanut oil as a flavour enhancer.
'Food manufacturers don't seem to be able to guarantee 100 per cent that there is no peanut or peanut oil derivatives in a product,' she says. 'We are not asking them to change the recipe, just to tell us what is in the food. Most oils and essences are exempted from food-labelling requirements because they appear in what are perceived to be insignificant quantities, 0.001 per cent. That, however, would be enough to kill my daughter.'
Natalie, 12-year-old daughter of Jane Peacock, of Crowthorne in Berkshire, has suffered from peanut aversion since she was a year old. She is also allergic to all other nuts and to latex and soya.
'I think she could say 'I am allergic to nuts' before she said anything else,' Mrs Peacock says. 'We try to make it not a problem but it's something you live with every day of your life. Natalie is not allowed to eat school dinners because there is a danger of her having a reaction at school.
'We have to be extremely careful when shopping. We like to eat out but we play Russian roulette - we have to go through the ritual of asking about all the ingredients.'
Susan Whyte, aged 19, from Scone near Perth in Scotland, has had 150 anaphylactic attacks since she was 15. She is completely confined to her parents' house and had to leave school early.
'To look at me now I am a picture of health,' she says 'but when I go outside . . .' If she even passes someone in the street who has eaten peanuts she will have an attack. 'It's an awful mental thing having to be stuck at home. You go through a lot of despair. I have lost a lot of self- confidence; sometimes I don't cope too well. I try to keep as busy as I can doing hobbies, painting, looking after the house.'
Since February, Marks & Spencer has begun sticking 'Contains Peanut' and 'Contains Nuts' labels next to the ingredient lists on all its nut products. Sainsbury's says it will in future be labelling all its products that contain nuts. And Sarah Reading has one small but important memorial in Debenhams' restaurants throughout the country: notices invite customers to ask for lists showing the ingredients of all their dishes.
The Anaphylaxis Campaign is at 34 George Road, Fleet, Hampshire. GU13 9PS.
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