A woman in the U.K. who was diagnosed with chronic idiopathic urticaria (CIU), or chronic idiopathic hives, said she is terrified that her debilitating symptoms may return at any moment since she isn’t sure what caused them to appear in the first place.

Lydia O’Connor, 23, said she was left with extremely swollen lips and an itchy full-body rash that lasted for six months and required several hospital trips. O’Connor told Caters News that she was finally diagnosed with the disorder last year after she spent four days in intensive care last year. She said the reaction had occurred previously when she was a teen, but it was diagnosed as a suspected nut allergy.

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But when her most recent reaction came on, she didn’t know what was happening to her body.

“My lips definitely doubled in size, it was terrifying because I didn’t know what was happening,” she told the news outlet. “When I was admitted to the ICU, I thought I was having a severe allergic reaction like anaphylaxis because I was struggling to breathe, and my tongue and lips were so swollen.”

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She told the news outlet that medication helped tame the swelling, but that it would continually return. The rash went away in August, but she lives in fear that it will return since she hasn’t been able to pinpoint a cause.

CIU is diagnosed when a patient experiences hives for the majority of six weeks or longer, according to the Journal of the American Academy of PAs. There often is no identifiable cause, and up to 50 percent of patients experience swelling of the skin, which O’Connor experienced in her lips and face. According to the journal, it is often difficult to treat due to the mystery of an underlying cause. Women are twice as likely as men to develop CIU, with most experiencing symptoms between ages 20 and 40.

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Treatment typically involves antihistamines and eliminating suspected causes or stimuli including extreme heat and cold, which is a concern for O’Connor. She said she’s nervous that her symptoms will reappear due to harsher weather circumstances.

“You could see people looking at my rash hoping they didn’t catch it,” O’Connor, who is training to be a paramedic, told Caters News Agency. “No one said anything until when I was on ambulance placement – where you wear short sleeves – so [you] could see my arms and chest. When I went to take someone’s blood pressure she told me, ‘Don’t touch me, I don’t’ want to catch it.”