She had warned staff she was allergic to shellfish, but they were used to make the dye being injected into her. As a result two consultants with a full range of resuscitation equipment stood by as it was pumped into her – and to their horror she suffered severe anaphylactic shock.

Her breathing stopped, her feet swelled up and her eyeballs popped out of their sockets before antidotes took effect. She has still not recovered completely.

The 61-year-old grandmother from Eckington, near Sheffield, carries adrenaline to tackle the symptoms and wears a MedicAlert bracelet detailing her allergy and another condition which causes sudden memory loss.

Her allergy is so severe that when she was bitten by sandflies that had been feeding on shellfish on a beach in Gambia, her ankles immediately became extremely itchy and within minutes her feet turned dark red. It rapidly reached her knees before being treated.

She said she was lucky to be alive because she told staff at Chesterfield Royal Hospital of the allergy only after her son-in-law had told her by chance the dye contained shellfish.

"I realised how serious it was. I'd gone for years without telling anyone in hospital I was allergic because I thought they weren't exactly going to feed me king prawns but if I hadn't it would have been too late for them to save me," she said.

The attacks occur without warning and last about 10 minutes until memories buried deep into her past are triggered. But on one occasion she was alone at home when she woke up and realised she knew nothing about anything about her.

She said: "It was dark and I just laid there. It was an hour before I dared leave the bed. I saw the doors at the top of the stairs and just felt there was something horrible on the other side.

There is no treatment for the condition which shuts off the part of the brain linked to memory but the attacks – believed to be linked to stress – stopped once she retired from her job teaching morality, ethics and world religions in school.

"If it happened in Africa I thought I might have to stay there and live there forever but when I got the bracelet it didn't worry me any more."

Her journeys there began five years ago when she went alone to Tanzania, where she helped set up water and electricity supplies, bringing books, paper and sewing machines to a remote village where locals had never seen a white visitor and speak only Swahili.

She said the bracelet gave peace of mind to her and her family with details of a 24-hour emergency line which can translate into 150 languages, and which advises on her conditions and next of kin. It has allowed her to travel to areas she never dreamed she would see and help thousands of people.

Sufferers with asthma, diabetes and severe allergies are among those who wear the bracelets or necklace pendants containing important information.

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