Mastocytosis | Symptoms


What are the symptoms of mastocytosis?

The symptoms are different, depending on where the extra mast cells are. If there are too many mast cells in your skin, you might have a red and itchy rash. You could get hives or have a rash that looks like freckles. If you rub the rash, it may get red and swollen. Sometimes the mast cells collect at one spot in your skin and cause one large lump.

If the mast cells are in your stomach and intestines, you might have diarrhea and stomach pain. However, this is a more rare form of mastocytosis.

In some people, the extra mast cells cause a serious reaction, similar to a bad allergy reaction. This kind of serious reaction is very rare. Their blood pressure may suddenly drop to a low level, causing them to faint. They may have trouble breathing. This reaction can cause death if treatment isn't started right away.

Possible symptoms of mastocytosis

  • Red, itchy rash
  • Rash that looks like freckles
  • Hives
  • One large lump on the skin
  • Diarrhea
  • Stomach pain, nausea or vomiting
  • Fainting
  • Difficulty breathing


Cutaneous and Systemic Manifestations of Mastocytosis by WA Alto, M.D., M.P.H., and L Clarcq, D.O. (American Family Physician June 01, 1999,

Written by editorial staff

Reviewed/Updated: 03/14
Created: 06/99