By Jane Elliott
Health reporter, BBC News
Margaret Edwards has a number of severe allergies and the wrong food or medication could make her very ill or even kill her.
Help is only a phone call away
She is also an asthmatic and has cerebral palsy and epilepsy.
But despite her numerous health concerns, Margaret, from Manchester, is supremely confident that if she collapses those treating her will know exactly what she can and cannot be given.
For she has her lucky talisman - a MedicAlert necklace - which she wears round her neck all day everyday.
The necklace is engraved with her main medical conditions and a personal number to allow her details to be accessed by those needing to treat her.
And she believes it has already saved her life. When she had an epileptic seizure and became unconscious during a lesson at her local swimming pool, medics were able to act quickly and confidently to save help her.
With just one call they were able to establish not only her medical health, but also confirm that she is allergic to gluten, dairy products and the painkiller codeine.
Margaret, 66, said: "I have worn my necklace for about 20 years now and I am so glad that I have it.
"I think it is a brilliant idea if you have hidden conditions like mine.
"Without them knowing what was wrong with me, I could have died if they had given me the wrong medication or treatment."
The necklace also gives details of next-of-kin so that they can be told what has happened.
This year the charity MedicAlert UK celebrates its 40th anniversary.
Their bracelets, necklaces and now watches, which can be bought from the charity once people have joined as members, are located at pulse points which would be checked first in an emergency.
Dr Marion Collins, who came up with the original idea after his daughter had an allergic reaction following a tetanus jab, had originally wanted to use a tattoo.
But Linda, his daughter, persuaded him to get her a bracelet, which he had engraved with the MedicAlert emblem and her condition.
Dr Collins had set up the American branch of MedicAlert in 1956.
MedicAlert is an international emblem
"I think I can save more lives with MedicAlert than I'll ever save with my scalpel," said the surgeon.
Jeanette Allen, chief executive, of the MedicAlert Foundation said: "From this acorn an oak has flourished.
"Now more than 280,000 people in the UK benefit from the reassurance and protection MedicAlert provides and our vision is that in years to come many more people in need will also benefit."
Recent research has shown that one in 10 has used their MedicAlerts.
The chief executive of the British Paramedic Association, Roland Furber, said that MedicAlert, used in 40 countries, has revolutionised the way patients are treated.
"We did manage before, but it was more difficult making clinical decisions.
"In an emergency it is essential that ambulance professionals receive as much information about a patient's condition as soon as possible.
"As a first port of call, all ambulance professionals are trained to look for medical identification.
"The MedicAlert symbol is an international emblem, recognised universally by healthcare professionals as identification for people who have various medical conditions.
"We fully encourage those who have a medical condition that puts them at risk to carry MedicAlert identification on them to protect themselves and help ambulance professionals."
MedicAlert advisers can be contacted on 020 7833 3034 or freephone
0800 581 420. Details on joining are also on its website.