Kourtney Kardashian Kourtney Kardashian

Kourtney Kardashian's infant son, Mason, is "doing fine" after he had an allergic reaction to peanut butter.

"Friday night Mason ate some peanut butter and had a little allergic reaction to it," Kardashian wrote on her blog. "He threw up within minutes of tasting it and got hives on his face."

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After the 31-year-old reality star called 911, her 11-month-old son was rushed to the hospital. "He was in good spirits the whole time and didn't even know anything was wrong," Kardashian wrote. "He even enjoyed riding in the ambulance. He's such a good boy!!"

"I learned such a lesson with this...to always follow my instincts and call 911. Always better safe than sorry."