Doctors are perplexed by a South Carolina woman who appears to allergic to almost everything she encounters.

Brynn Duncan, 21, tells CNN her puzzling condition makes her feel like she is living life “in a bubble,” because of the vast number of things that provoke allergy-like reactions.

Shortly before her 16th birthday in 2010, Duncan had her first serious allergic reaction after eating an ice cream treat. Since then, her life has been a blur of sick days and doctor appointments.

CNN reports that she has been diagnosed with a range of conditions, none of them definitive. Among them: digestive disorders, muscle problems, blood pressure abnormalities, and even connective-tissue irregularities.

But her own research — confirmed by her current doctor — suggests she has something called mast cell disease, which is characterized by mutations in mast cells that cause abnormal immune system reactions.

As a result, Duncan is allergic to fruit, vegetables, milk, soy, nuts, smoke, perfume, and many other things.

"There's a lot of guilt that goes along with having a chronic illness," Duncan said. "You feel like a burden. And people can tell you you're not, but no matter what, in your head, you feel that you are."