Solitary mastocytoma (1870)

Key points below

What is a Solitary Mastocytoma?

Solitary Mastocytoma is a common skin condition that can affect any part of the body.  Most often it affects the arms, neck and trunk. It is a round, flat to slightly raised, red to brown colored spot. The spot is not painful, but may itch.  Sometimes the spot will form a blister or a hive when rubbed or scratched.  A hive is a type of rash that is red, raised and often itches.  Most of the time there is only one spot but some children may have more.


What causes it?

The exact cause is not known.

There are mast cells in most parts of the body. They help fight infection and make a substance called histamine.  Mast cells release histamine in the skin.  Histamine causes hives, itching and the red color of a rash. Solitary Mastocytoma occurs when there are more mast cells in the skin than normal.  Many skin conditions have extra mast cells in the skin.    

How is it diagnosed?

Your child’s signs and symptoms help the doctor make the diagnosis.  A skin biopsy is normally not needed. 

How is it treated?

How long does it last?

Solitary mastocytoma will most likely go away without treatment as your child grows.  It can take many years.  The redness and itching normally go away before the spot goes away.  There are less and less symptoms as your child gets older.

Special instructions



Call your child’s doctor, nurse, or clinic if you have any questions or concerns or if your child has:

  • Itching that gets worse even with medicine.
  • Special health care needs that were not covered by this information.