Further reading

Akin C. Mast cell activation syndromes. J Allergy Clin Immunol. 2017;140(2):349-355.

Molderings GJ, Haenisch B, Bogdanow M, Fimmers R, Nöthen MM. Familial occurrence of systemic mast cell activation disease. PLoS One. 2013;8(9):e76241. Published 2013 Sep 30.

MCAS forms part of a spectrum of mast cell disorders. The relationship between the conditions which fall within this spectrum is complex, and it is becoming clear that patients with MCAS may also have other mast cell disorders such as mastocytosis or hereditary alpha tryptasemia syndrome (HATS). Mastocytosis is a primary or clonal mast cell disorder characterised by an increased number of mast cells throughout the skin and internal organs. HATS is a newly recognised condition caused by the elevated production of tryptase. Since the genetic causes of mastocytosis and HATS are well-characterised, genetic tests for these conditions are available and these mast cell disorders are often more straightforward to diagnose.


Ruth to provide >

Recognising anaphylaxis Anaphylaxis refers to a serious allergic or hypersensitivity reaction which can affect multiple body systems and can range from mild to severe (potentially life-threatening). The specific triggers of anaphylaxis vary between individuals and in some cases the trigger may be unclear (these cases are referred to as ‘idiopathic’).

Common triggers include foods, stinging insect venoms and drugs. Given the sudden onset and potentially fatal consequences of anaphylaxis, it is important to quickly recognise the typical signs and symptoms of these reactions.

Anaphylaxis is highly likely when the following signs are present:

  1. Rapid onset (within minutes to hours) of symptoms involving the skin or mucosal tissue (skin lining the body cavities e.g. inside the mouth and nose) for example, swollen lips or tongue
  2. Breathing difficulties
  3. Reduced blood pressure, collapsing, incontinence (lack of bladder control)
  4. Persistent gastrointestinal symptoms such as cramps, abdominal pain or vomiting

The burden of symptoms on people suffering MCAS can be substantial. The potential severity of symptoms paired with the unpredictability of triggers can mean that the everyday lives of people with MCAS, their families and carers are considerably impacted. Without a confirmed diagnosis and treatment to stabilise mast cells or block mediator effects, triggers and symptoms can become severe, more frequent and unpredictable.


Observational studies and patient-reported data show ‘clustering’ of MCAS with other conditions, meaning that people who have MCAS often also have at least one additional condition. Common comorbidities include type 2 diabetes, Ehlers Danlos Syndrome (EDS; a connective tissue disorder), and dysautonomia/postural orthostatic tachycardia syndrome (POTS). The relationship between MCAS and many of these comorbidities is yet to be fully understood, and more research is required.

Further reading

Theoharides TC, Tsilioni I, Ren H. Recent advances in our understanding of mast cell activation - or should it be mast cell mediator disorders?. Expert Rev Clin Immunol. 2019;15(6):639-656.

Afrin LB, Ackerley MB, Bluestein LS, et al. Diagnosis of mast cell activation syndrome: a global "consensus-2". Diagnosis (Berl). 2020;/j/dx.ahead-of-print/dx-2020-0005/dx-2020-0005.xml.

Simons FER, Ardusso LR, Bilò MB, et al. International consensus on (ICON) anaphylaxis. World Allergy Organization Journal. 2014:7-9.

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