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  • Writer's pictureIt’s Complicated

What is mast cell activation syndrome ?



Mast cell activation syndrome (MCAS) is a form of Mast Cell Diseases and is caused by ‘abnormal mast cells or abnormal release of chemicals contained within them.’ (PoTS UK)

Mast cells are a type of blood cells found in in our body tissues and they help the immune system fight infections and help with injuries, by releasing chemicals known as mast cell mediators.

MCAS can be quite common in those with PoTS and hypermobility / HEDS, for reasons not well known.

Below is an image to show how mast cells can affect the body during a response.

Image from

Some of my symptoms include :

  • Hives

  • Swelling

  • Wheezing

  • Nausea

  • Writing in the skin

  • Headaches

  • Itching

  • Abdominal cramps/stabbing

  • Upset stomach

  • Bladder inflammation

Treating MCAS includes anti-histamines, both H1 and H2 hi stamina blockers and mast cell stabilisers. Thes

e are the first step in treating MCAS as well as diet changes and identifying triggers and making lifestyle changes accordingly. For some, these treatment options don’t work and injections may be offered such as anti IL5/5a. This would be done in certain cases where all other treatment option and lifestyle changes have not been effective and the symptoms are progressing/ are quite frequent.

Some of my triggers include :

  • Alcohol

  • Certain foods

  • Detergent

  • Make up / skincare products

  • Cleaning products

  • Heat / cold

  • Stress

  • Exercise

  • Medications

  • Sun

  • Hay / tree pollens

  • Dust

It can be difficult to diagnose MCAS as symptoms can be broad and be caused by many other things. Diagnosis is therefore based on symptoms, how recurrent they are and how severe, blood tests and the effectiveness of anti histamines.

Information from


- Personal experience


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