MCAS and Eating Disorders: When “Just Eat” Can Make Things Worse

She’s 13. She has hypermobile Ehlers-Danlos syndrome (hEDS), mast cell activation syndrome (MCAS), and an eating disorder.

She was admitted to a residential treatment facility where the staff, well-meaning and well-trained in eating disorders, insisted she eat the foods on her tray.

Every single one.

Within hours, she was flushing, cramping, and nauseated. Her body was doing exactly what it had done before in response to suspected mast cell triggers.

But the treatment team saw something else: resistance. Anxiety. A patient who “wasn’t ready to recover.”

This is a collision I see in my practice, and I believe it represents an important blind spot in eating disorder treatment.