Recognition and Management of Medication Excipient Reactivity in Patients With Mast Cell Activation Syndrome

Am J Med Sci. 2019 Jun;357(6):507-511. doi: 10.1016/j.amjms.2019.03.005. Epub 2019 Mar 22.


Mast cell activation syndrome (MCAS) is a complex disorder hallmarked by chronic multisystem inflammatory, allergic and growth dystrophic phenomena caused by inappropriate mast cell activation. MCAS has been estimated to affect as many as 17% of the population with a severity ranging from mild to life-threatening. MCAS patients are more sensitive than the average person to chemicals in the environment, including the nondrug ("inactive") ingredients (excipients) in medications and supplements. Excipient reactivity may explain unusual side effects to medications health professionals often find puzzling, such as the patient who appears intolerant of prednisone, acetaminophen, levothyroxine, or a vitamin. We present a series of patients with MCAS to illustrate important points regarding excipient reactivity which may be useful in everyday practice.

Keywords: Chemical sensitivity; Ehlers-Danlos syndrome; Excipient; Mast cell activation syndrome; Postural tachycardia syndrome.

Publication types

  • Case Reports
  • Review

MeSH terms

  • Adolescent
  • Excipients / adverse effects*
  • Female
  • Humans
  • Male
  • Mastocytosis / chemically induced*
  • Middle Aged
  • Young Adult


  • Excipients