People with severe allergies have to carry an adrenaline pen for emergencies
A quarter of a million adrenaline pens - a potential lifesaver for those with severe allergies - will have run out by January, a charity is warning.
The Anaphylaxis Campaign is urging the 210,000 British people who carry these injectors to check their expiry date urgently if they have not done so.
Most pens used in the UK are US-made Epipens and tend to arrive in one large batch with the same expiry date.
But the numbers about to expire are unprecedented, the charity says.
Anaphylaxis is a severe, potentially life-threatening allergic reaction which can be sparked by anything from latex to peanuts.
It requires immediate treatment as symptoms such as swelling, breathing problems, increased heart rate and loss of consciousness, develop rapidly.
About 210,000 patients in the UK are prescribed adrenaline injectors for this scenario - the chemical raises the body's blood pressure and brings down the swelling.
Many people keep three pens in different locations. But 234,000 Epipens - the principal brand prescribed in the UK - will expire in December and January.
This is due to a combination of factors. Many pens, which have a shelf-life of 18 months, were prescribed in the summer of last year and they all came from the same batch with this winter expiry date.
It is unclear how many people have already checked and obtained new pens, but the Anaphylaxis Campaign said this time of year was a particularly "hazardous" one for those with allergies to start with amid Christmas and New Year parties with different foods on offer.
"We certainly don't want to stop people having fun over the coming weeks; we are simply suggesting that extra care is taken so everyone can enjoy themselves over the party season safe in the knowledge they are well prepared and this includes checking that adrenaline injectors are in date and they are carries at all times," said Lynne Regent.
The head of the charity Allergy UK also urged allergy sufferers to take extra care.
"It is very important that people who need to carry an auto-injector are vigilant all the year round about the expiry date as it is something very easy to overlook given that thankfully it is not in regular usage," said Muriel Simmons.
Paediatric allergist Dr Adam Fox said: "Patients who are at risk need to be prepared to deal with a reaction when it occurs and in the case of nut allergies in particular, reactions seem to be more common around the festive season.
"It is vitally important that anybody who is prescribed an adrenaline injector has been shown how to use it and carries it with them at all time, as well as checking that it is in date - it may just save your life."