A woman who suffers from a rare allergy to exercise has revealed how having sex with her husband could potentially kill her.
Katy VanNostrand visited a series of doctors after repeatedly going into anaphylactic shock over a six-year period.
She was finally diagnosed with exercise-induced anaphylaxis in around 2009 after having "between 15 and 20 reactions a year".
Now, the 34-year-old says exertion - from a brisk dog walk or a long run to "vigorous sex" - could make her collapse.
“I still love exercising, but there have been a couple of times that have been really scary and I’ve thought I might die,” Katy said.
For years, the nurse, from Colorado, US, found herself suddenly going into anaphylactic shock - which can prove fatal.
She would have to rush to hospital for epinephrine medication, vitals monitoring and life-saving antihistamine treatment.
But, despite repeated incidents, doctors struggled to find the trigger.
Katy's first reaction occurred when she was a 22-year-old college student, undertaking religious studies at Bates College, in Lewiston, Maine.
At the time, she was out running with her friend.
Katy, who has frequent extreme reactions after exertion, explained: “I was running and suddenly I started to feel really terrible.
"We stopped and I thought I must be really dehydrated or something. I pulled up my shirt and my friend looked at me and said 'Oh my gosh'.
“My face and lips were swollen and my eyes were swelling so much. I was also covered in deep red hives.
“We ran to the local hospital and they said I was having an anaphylactic reaction, but it could be anything that caused it.
“Something I ate or maybe my washing powder. After that, this started happening pretty frequently. I had between 15 and 20 reactions a year.“From 22 until I was about 28, I saw loads of doctors, but no one knew what it was.”
For years, the reactions continued and Katy went from doctor to doctor, but they couldn’t find the cause.
After moving from Golden, Colorado, to Carbondale with her husband John, 35, who is also a nurse, Katy wanted to make some new friends.
She decided to join a gym with her neighbour.
But within 10 minutes running on the treadmill, her face started swelling and she was rushed to A&E at Valley View hospital in Glenwood Springs.
There, a doctor referred her to a new allergist.
Initially sceptical, but desperate for answers, Katy agreed to see him and within a few minutes, he told her he suspected she had exercise-induced anaphylaxis.
The ultra-rare condition means that if Katy eats certain foods, her body goes into shock when mixed with the hormones released when her heartbeat rises.
She has had to cut grapes, cranberries, oats, corn, rice, onion, celery, fennel, nuts and even black pepper from her diet, in a bid to control the reactions -because any physical activity after eating them can leave her seriously unwell.
“Exercise for me can mean anything from going for a brisk walk with my dog, to a long run or even vigorous sex can trigger it,” she said.
Katy has to carry an Epipen – an emergency injection which controls the symptoms of anaphylactic shock - in case her throat starts to swell and she stops breathing.
“One occasion I’ll never forget happened back in August 2011," she recalled.
“My husband and I lived in Alaska and I had run for about an hour out on this trail, when I started having a reaction.
“John was working a night shift, so he was asleep. There was no one around and I knew he wasn't going to wake up.
“My face was swelling and I was struggling to breathe, but I was just about able to drive myself to an emergency room. It was very scary.”
An avid runner, Katy is determined to carry on exercising.
She completed her first marathon in November last year - after two failed attempts because she suffered a reaction.
She said: “To get through a race, I make beef jerky, so I know exactly what has been put in it. I got some squeezy baby food packets that you can fill yourself.
"I have been mixing orange juice with chia seeds in one of those. It doesn't fill you up, but it gives you enough glucose for the race.
“I completed my first successful marathon in November 2016. I signed up for three, but couldn’t run in them, because of reactions a few days before.
“If I have one, I’m more likely to have another one soon after.
“Finally completing a marathon was a lot of work, but it was awesome. ”
Cutting out food and taking medication means that Katy now has a reaction about four to six times a year.
However, she is worried that they are becoming increasingly unpredictable, so her doctor has recommended that she never runs alone.
She said: “It is fairly manageable now, as I have about four to six a year, but according to my allergist, that is unacceptable.
“Cutting out certain food lowers the risk but sometimes it is just that I am allergic to the chemicals that are produced by your body during exercise.
"You can never control it 100 per cent.
“I need to exercise so I am working with my allergist to make sure we do what is best to keep me safe.”
Anaphylaxis is a serious allergic reaction that can be potentially fatal.
Anaphylaxis UK said: “Exercise-induced anaphylaxis is an uncommon, potentially-serious condition in which anaphylaxis (a severe allergic reaction) occurs during or after physical activity. It is a complex condition that needs an expert diagnosis and clear advice. A specialist will be able to consider what treatment is necessary.”