The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 21

I answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.

30. Why does my skin get red and itchy?
• Flushing is one of the hallmark signs of mast cell disease. It is sometimes the symptom that drives providers to look at mast cell disease as a potential diagnosis.
• Mast cells make and release many chemicals. These chemicals are commonly called mediators because they mediate many reactions in the body that affect the body in many different ways.
• Some mast cell mediators make blood vessels relax. The vessels get a little wider. When the vessels get bigger, the ones under the skin get closer to the skin. Because those vessels show red from the blood in them, the blood is closer to the skin so the skin looks red.
• Flushing is often asymmetrical. There isn’t a hard and fast reason for why this happens but is likely caused by local mast cell mediator release. Essentially, if the mast cells on the right side of your face get irritated, the right side is more likely to flush than the left side.
Flushing is mostly mediated by prostaglandin D2. Aspirin is often prescribed for mast cell patients that tolerate it because aspirin blocks cells from making prostaglandins. This is because aspirin interferes with the molecule that manufactures them. Many other substances can also interfere with this, including other NSAIDs. Another class of drug, 5-lipoxygenase inhibitors, can also stop production of prostaglandins in a different way.
• To a lesser extent, histamine contributes flushing and antihistamines sometimes help.
What exactly causes itching is still not entirely clear. There are special little places in your body called itch receptors. When they notice something itchy, it’s their job to raise the alarm. We think that mast cells carry the message from those places to the nervous system that then spread the itch signal. It’s like carrying the flame of one candle from the itch receptor to the nervous system, which sets the forest on fire.
• Hydroxyzine and other antihistamines are often used for itching. Corticosteroids like prednisone, either oral or topical, may help. Also, medications that interfere with prostaglandin production, like an NSAID or a 5-lipoxygenase inhibitor, sometimes help.

For more detailed reading, please visit these posts:
The Provider Primer Series: Management of mast cell mediator symptoms and release
Prostaglandins and leukotrienes
Mast cell mediators: Prostaglandin D2 (PGD2)