Skip to main content

Urticaria Pigmentosa (Mastocytosis of the Skin)

What is Urticaria Pigmentosa (Mastocytosis of the skin)?

Urticaria Pigmentosa (UP) is an uncommon rash that affects the skin of infants, children and young adults. The rash is made up of reddish-brown spots called mastocytomas that are flat or slightly raised and may form hives when they are rubbed or scratched. Sometimes the spots will blister. There may be a few spots or many spots. The lesions usually are most prominent on the trunk, but can occur on the scalp, face and extremities.

How does UP affect your child?

The rash of UP is not painful but does cause itching in some children. Massive histamine release can cause headaches, flushing (redness of the skin), diarrhea, vomiting, wheezing (breathing hard with a whistling sound), increased heart rate and a decrease in blood pressure. These symptoms are rarely observed in young children with UP. Please let your doctor know if your child experiences any of these symptoms.

How long does UP last?

Most infants and children will outgrow UP as they get older. New spots may continue to appear as long as the condition lasts. There is no known treatment to prevent new spots from appearing. The reddish-brown spots may fade as your child grows older but usually last for years.

Special considerations

In some cases your doctor may suggest the following:

  • Your child’s primary care doctor, dentist, child care provider and school be provided with a copy of this information. You may also want to keep a copy of this information in your car or purse in case of emergency.

  • Your child wear a medical alert bracelet that reads: “Urticaria Pigmentosa (Mastocytosis).”

  • If your child has surgery or visits the emergency room, the doctors be informed of your child’s UP and given a copy of this information.

UP Treatment 


  • If your child is not having any associated symptoms/problems, it may not be necessary to give any medications.

  • If your child has symptoms of itching, your doctor may choose to treat your child with an antihistamine. An antihistamine is a medicine that is used to decrease the release of the histamine from mast cells.

  • Sun exposure may increase the reddish-brown color of the rash. Applying a sunscreen with SPF of 30 or greater may help to prevent the spots from becoming darker. 

  • If the rash becomes dry, scaly or rough, apply a moisturizing cream or ointment 3-4 times a day.

  • Triggers do not cause UP but they may bring out the rash or make the rash worse. In rare instances, massive release of histamine in the skin can cause low blood pressure, flushing, or even shock. You will need to avoid things that trigger the release of histamine.

How to avoid UP triggers

There are a number of things that can trigger the rash of UP. Some of the triggers include emotional stress, medicines, foods, and physical stimuli.

Possible Triggering Drugs

  • Aspirin

  • Opiates: morphine, codeine

  • Alcohol

  • Dextromethorphan

  • Polymyxin B (found in many topical antibiotics)

  • Thiamine (a vitamin)

  • Quinine

  • Dyes that are used to take X-rays

  • Certain anesthetic agents

Physical stimuli

  • Physical stimuli are mechanical or external factors that cause an increase in the release of histamine: exercise, vigorous rubbing of the skin after bathing or showering, hot baths, drinking hot liquids, spicy foods, sunlight, cold exposure.