WARNING: GRAPHIC IMAGE BELOW

A UK woman claims she developed sepsis — and could have lost her leg — after a blister formed on her heel from a pair of second-hand sandals.

Gemma Downey, of West Sussex, England, walked to a local train station last week while wearing a pair of platform sandals she purchased from a thrift shop. Shortly after, the 23-year-old claims she developed a “strange colored” blister on her heel.

“It started off as my shoes rubbing on the back of my foot, it sort of broke the skin, like a cut,” Downey said, according to the Daily Mail. “'At some point, it looked like it was forming a tiny blister.”

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“'I started noticing I couldn't walk properly and was limping and was in pain a lot more than normal. My foot had swollen right up and [the swelling] was traveling around my ankle area, and the pain was absolutely awful,” she added. “I just dropped to the floor in agony, it was getting more and more swollen.”

Not long after, the young woman’s symptoms worsened — she claims she began to vomit and had trouble breathing.

“I had pains all over my body, I had chest pain and trouble breathing, I knew something was seriously wrong. I went to a doctors' appointment and he said my heart rate was sky high, my blood pressure was really, really low, [and] my temperature was high,” Downey continued.

“My skin had started getting blue and that's point the blister got a lot bigger,” she added.

Downey claims the doctor she saw then told her to go to the hospital, as she was likely experiencing sepsis — or what the Centers for Disease Control and Prevention (CDC) says is “the body’s extreme response to an infection.”

Though a person’s body “normally releases chemicals into the bloodstream to fight an infection,” per the Mayo Clinic, sepsis occurs when “the body's response to these chemicals are out of balance, triggering changes that can damage multiple organ systems.” Signs include a high heart rate, and fever or shivering, according to the CDC. Symptoms can include shortness of breath, extreme pain, and sweaty skin.

Downey, who works as a model, was hospitalized for two days to clear the infection. Doctors aren’t sure what triggered the sepsis, per the Daily Mail.

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“I was told I was showing early stages of sepsis but thankfully I was able to get treatment before it could escalate to anything further,” she said. “I know it can be fatal. The doctors told me I was lucky I had acted on it and went to check it out because it could have been more serious.”

For the next few months, Downey is limited to backless shoes — such as flip flops — while her injury heals.

“I couldn't believe something so insignificant could cause so much damage,” she added.