The 33-year-old Liberal Democrat MP for East Dunbartonshire said her life was saved by doctors at Glasgow’s Southern General Hospital, who treated her after she collapsed, struggling for breath.
Ms Swinson, who has a nut allergy, started to experience a reaction on Saturday as she was driving home from a cake sale in Bishopbriggs Girl Guide Hall in her constituency, held to raise funds for the military charity Help for Heroes.
The MP told The Scotsman she was eating the biscuit in her car when she suddenly started to feel ill.
She said: “Almost instantly I felt a tingling sensation so I knew I had unknowingly eaten a nut. It’s difficult to always know whether something contains nuts or not – and this time I got it wrong.”
I immediately drove home and took some antihistamine.
“After a while the symptoms were getting worse and my face started to swell, which meant that my body was going into anaphylaxis shock.”
Anaphylaxis is a serious allergic reaction that if untreated, can be fatal.
The MP telephoned her mother, who took her to hospital. Ms Swinson said: “I had taken the precaution of writing out what had happened in case my throat swelled up so much I couldn’t speak.”
Hospital staff injected her with an EpiPen, which contains adrenaline, which reverses the effect of anaphylaxis. She was also given steroids and put on oxygen, and kept in overnight to make sure she did not suffer any further adverse reactions.
The MP said: “It was a very scary experience. Luckily, once you get the right treatment you recover very quickly from it – but the bottom line is that if you don’t get help, you can die.”
She said she had had a nut allergy for 30 years and had experienced a variety of reactions, “but this was quite terrifying”.
Ms Swinson, a former parliamentary private secretary to Deputy Prime Minister Nick Clegg, was discharged from hospital yesterday morning and later travelled to London.
She posted a message on her Facebook page, praising the medics who had helped her.
She wrote: “Thanks to the fab staff at the Southern General Hospital for saving my life.”
Ms Swinson, who is married to fellow Lib Dem MP Duncan Hames, also urged anyone with a nut allergy to take precautions.
“The message I would really like to put out is that anyone with a nut allergy should always carry an EpiPen. They should also make sure their friends know what to do to treat them.”