Cutaneous Mastocytosis: Brown Spots That Itch and Swell
Urticaria pigmentosa is the most common skin form of mastocytosis, a condition in which too many mast cells collect in the skin. It is not ordinary hives. Instead, reddish-brown spots or bumps appear that can itch and turn into a welt when rubbed.
Symptoms
- Tan, red-brown or yellow-brown spots or small bumps, usually on the trunk and limbs
- Itching, flushing or blistering, especially in infants
- Darier sign: a spot that swells and reddens after being rubbed
- Triggers such as heat, friction, certain medicines and illness
Children vs Adults
It most often begins in infancy or early childhood, and in many children the spots fade by adolescence. When it starts in adults, doctors are more likely to check for systemic mastocytosis, which involves other organs, with blood tests such as serum tryptase.
Diagnosis
A dermatologist examines the skin and may take a small biopsy. Do not rub or scratch spots before an exam, since this can cause flares. For comparison, see how ordinary hives are described in what are hives.
Care and Treatment
Treatment aims to control symptoms: daily non-sedating antihistamines, avoiding known triggers, and sometimes topical steroids or other medicines. Families are often advised to discuss medication choices, including certain pain medicines, anesthesia and contrast agents, with the care team. Related: urticaria.
When to Call 911
Call 911 or go to the nearest emergency room right away if hives come with trouble breathing, wheezing, tightness in the throat, swelling of the tongue or lips, dizziness or fainting. These can be signs of anaphylaxis, a severe allergic reaction that needs immediate treatment.
When to See a Doctor
See a doctor if your symptoms last more than a few days, keep coming back, cover large areas, or interfere with sleep or daily life. The Hives Treatment Center, founded by Dr. Tiffany Young, is a San Francisco practice that evaluates and treats mast cell and skin conditions in person and online.
Related Reading
You may also find these guides helpful: causes of hives and hives symptoms.
Frequently Asked Questions About Urticaria Pigmentosa
Is urticaria pigmentosa cancer?
It is a mast cell disorder, not a typical skin cancer. Systemic forms need specialist care.
Will my child outgrow it?
Many do, and lesions often fade through childhood and puberty.
Why is it called urticaria?
Because the spots can swell and itch like hives when rubbed or triggered.
Get Relief for Your Hives
Brown, itchy spots that swell when rubbed should be evaluated. Visit our hives treatment page to see the latest treatment options for your outbreak.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. If you think you are having a medical emergency, call 911.
