What began as a simple change in a COPD inhaler turned into an unexpected medical mystery. Within two days, a 55-year-old woman developed “intensely painful, bright red patches” on her face and neck, along with a mild fever. When her symptoms quickly faded, doctors were surprised to find the biopsy showed Sweet syndrome—a rare, immune-related skin disorder.

The woman had long managed COPD and hypertension with enalapril and a formoterol inhaler. But after switching to an indacaterol-glycopyrronium inhaler, she developed the rash within 48 hours. She denied new cosmetics or diet changes but reported sun exposure. Once she stopped the new inhaler and started corticosteroids, her symptoms improved “within two days.”

Sweet syndrome, also known as acute febrile neutrophilic dermatosis, causes sudden, painful red plaques—often on the face and upper body—along with fever and high white blood cell counts. It’s typically linked to infections, cancers, or medications like antibiotics or vaccines.

This case is unique because “inhaled therapies have never before been documented as a trigger.” By excluding other causes such as lupus or dermatitis, doctors concluded the inhaler was the likely cause—raising new concerns about the hidden risks in common respiratory treatments.