JUST ONE CUP OF WATER COULD KILL LITTLE HEIDI; Girl's deadly allergy means she cannot weep, wash, drink, play or even stand in the rain.
One small drop on her skin brings her out in blisters in seconds.
And even her tears can leave her cheeks red and cracked.
Heidi, nine, is one of the few people in the world with a water allergy so violent it could kill her.
She cannot DRINK it, BATHE in it or go out in the rain and SPLASH in it.
And now in a world-first operation, surgeons have removed Sarah's appendix using virtually no water-based products.
Water accounts for 80 per cent of the human body and in effect Heidi is allergic to HERSELF.
Her sweat, blood, saliva and urine all leave nasty blisters if they come in contact with her skin.
Heidi survives by drinking four small glasses of milk or orange juice a day and eating dry foods like biscuits and chicken.
But even then, if her body takes in too much moisture it reacts and she is sick.
Heidi once drank a mouthful of water by mistake and her body went into shock which was only reversed by a dose of adrenaline.
The condition - known as aquagenic urticaria - is incurable. It is not genetic but a fluke of nature.
Heidi's life is one constant round of trying to avoid contact with water.
Mum Wendy, 35, and her printer husband Dave, 39, hold her upside down over the bath to wash her long curly red hair.
Bath-time is a 30-second dip once a week. The blisters from this brief contact with water last for around an hour.
She is allowed a thimbleful of water when she brushes her teeth. Breakfast is a bowl of dry cereal and a slice of toast.
Lunch is two slices of dry ham.
Her evening meal is usually chicken or beef with mashed potatoes, but no gravy.
Ice lollies and slushy ice drinks are banned.
Even though Heidi is tall for her age, slim and has beautiful bright blue eyes, her mum is set against making a celebrity out of her daughter.
Wendy, whose other daughter Sadie, five, has no allergies, said: "A model agency approached us after Heidi's picture appeared in a magazine.
"They offered everything, including private education for her, if we let them sign her up.
"But I told them straight away that is not what we want.
"Our biggest dream is for her to go swimming and be a normal child. She is a little girl with an allergy, not a TV star."
Although swimming is out of the question for Heidi, she can go out in the rain in a water-tight suit specially designed for her at a cost of pounds 1,200.
Made from a fabric that allows her skin to breathe, it protects her from head to foot and has waterproof seams.
Earlier this year it was stolen when thieves broke into Wendy and Dave's two-bedroom home in Tividale, West Midlands.
After Heidi appealed for its return, the callous thugs left it in a carrier bag on their doorstep - cut to bits.
Heidi's allergy has financially crippled Wendy and Dave.
They have taken out a second mortgage to cover the cost of trying to find out what was wrong with her.
"I am not ashamed of our debts because every penny has gone on Heidi," said Wendy.
"I spent every day travelling somewhere to try to find out the problem.
"I completely wrapped myself up in her.
"When the specialists said she couldn't be allergic to water, I searched for the answer elsewhere. It was an obsession. I saw Chinese herbalists, naturopaths, everyone.
"Our bills and credit cards were sky-high and we took out a pounds 15,000 loan on top of our pounds 21,000 mortgage.
"We must have at least six county court judgements against us."
When Heidi was born she was covered in blisters.
Wendy said: "I remember her kicking like mad inside me.
"I believe she was reacting against the fluid in my womb. When she was born she had a rash all over.
"The midwife said it was a heat rash.
"I saw specialist after specialist who didn't know what was causing it." Then when Heidi started school, the doctor there was convinced - like Wendy and Dave - that Heidi's problem was water.
"That is how we eventually got the diagnosis when she was five," said Wendy.
Heidi recently had an emergency operation to remove her appendix. Surgeons at Shrewsbury Hospital had no experience of her condition. They contacted Birmingham City Hospital, where Heidi is a patient of allergy specialist Dr Dinakantha Kumaratne.
Wendy said: "The surgeons had to think very fast about what they were going to do. They were marvellous."
After the operation Heidi's tears left her face red and blistered.
She also developed giant blisters all over her body caused by the reaction to a water-based drip.
Now recovered, Heidi has accepted an invitation from the Duchess of York and her daughters Eugenie and Beatrice to have tea tomorrow at their home in Surrey.
Wendy admits Heidi's allergy has put a strain on her marriage.
She says: "There are times when I have felt a little bit left out.
"Dave naturally dotes on Heidi, everyone in the family does and I have felt a bit unloved. But we have got through difficult times and we are setting up a charity for victims of rare allergies.
"The hospital can't even tell me what the future holds for Heidi because they do not know themselves.
"Maybe she will grow out of it. We don't know."
And until then, Wendy and Dave cannot even kiss their daughter goodnight - because their saliva will leave a red mark in the shape of two lips on Heidi's face.