A mother in the U.K. is hoping her son’s terrifying sepsis ordeal may help spare others from the same fate after she snapped a photo of a red line that had started creeping up the inside of his wrist following a fall at the zoo.

“If you spot this red line running from a wound along the vein get yourself or your child seen straight away,” Alexandra Ruddy, Ewan Ruddy’s mom, told SWNS. “Ewan was fine in himself, he was happy – which is what made it difficult to notice. He was absolutely fine and that is the scary bit about it.”

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Ruddy said it all started with a fall at the zoo on June 1, but that Ewan only suffered a small scrape on his hand, elbow and knee that didn’t require major medical attention. Ruddy said she and her husband cleaned his cut at home and put a bandage on it, but that it didn’t “look infected” or “gunky.”

About a week later, Ruddy told SWNS that her son developed a fever, and that he started complaining about a red mark on his wrist that was “itchy.” She took him to an off-hours pediatrician, who confirmed it had developed into sepsis.

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“He put a black marker on the line and said it gets wider or bigger than this line you need to come back immediately,” Ruddy told SWNS.

Ewan was prescribed antibiotics, which quickly began clearing the infection. Ruddy said she posted the photo to Facebook with the encouragement of her husband, because a similar post she had seen two years ago helped her recognize the signs of infection in her son. Ruddy’s warning has been shared more than 37,000 times since she posted it on June 2.

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Sepsis is a life-threatening condition is the body’s extreme response to an infection. It occurs when an infection in the skin, lungs, urinary tract or elsewhere in the body triggers a chain reaction. Without timely treatment, it can lead to tissue damage, organ failure and death, according to the Centers for Disease Control and Prevention (CDC).