Mast Cell Activation Syndrome (MCAS)

Frequently Asked Questions

MCAS is a type of mast cell activation disorder characterised by abnormal activation of mast cells resulting in chronic multi-system poly-morbidity of a general inflammatory nature, with or without an allergic nature.

In the skin, mast cell numbers are highest in the upper dermis and their numbers are not affected by age or sex but increase in response to various environmental stimuli as shown after ultraviolet radiation in human skin and after exposure to topical sensitizing agents. It is thus obvious that mast cells constitute an inherent component of numerous skin conditions including sensitivity, itching, rashes, breakouts, acne, pigmentation, rosacea, melasma, and even some auto-immune conditions which affect the skin.

While we need mast cells to protect us from threats, they become a problem when they are overactive and hyper-responsive and will not ‘turn off'.

When these hyper-responsive Mast Cells are activated, they release over 200 signaling chemicals (e.g. histamine, prostaglandins, leukotrienes, cytokines, and chemokines) which cause INFLAMMATION.

  • Feeling as though you have been sick forever 
  • The trouble with allergies and asthma 
  • Overreaction to insect bites, bee stings, and chemical intolerances 
  • Facial and chest flushing 
  • Skin rashes that come and go, including hives and angioedema 
  • Skin conditions such as eczema dermatitis, rosacea, and melasma/hormonal pigmentation  
  • Itchiness and a burning feeling 
  • Brain fog and headaches/ migraines  
  • Insomnia is especially waking up at 3 AM (due to high histamine levels )  
  • Poor wound healing and easy bruising 
  • Waxing and waning of symptoms 
  • Ear problems such as Eustachian tube dysfunction, tinnitus 
  • Feeling of Vibration in body / restless leg syndrome  
  • CIRS Chronic  Inflammatory Response Syndrome  

MCAS may be mild in some people and only exacerbate in response to a significant life stressor. In others, symptoms may develop from a young age and slowly become worse over time.   

People with MCAS are likely to experience a few of the most common symptoms. Because mast cells are located throughout the body, symptoms can affect the eyes, nose, ears, throat, skin, heart, blood, lungs, gastrointestinal tract, and the nervous, endocrine, and musculoskeletal systems. 

The symptoms of MCAS are often confusing. For a long time, many people with MCAS have been told that their condition was psychosomatic or ‘in their head’. Fortunately, awareness of this frustrating and debilitating condition is spreading. Testing for MCAS is somewhat complex and confusing, as positive biomarkers may only be observed when a patient has a flare-up. Symptoms of MCAS can also Wax And wane (i.e. the symptoms can come and go) 

Mast cells are present in the skin and every mucosal surface (eg. respiratory tract and gut)  

  • Melasma/hormonal pigmentation  
  • Chronic Dermatitis/Eczema 
  • Rosacea  
  • Psoriasis  
  • Urticaria  

The Chemical mediators which are released when Mast cells are triggered cause inflammation. Hormonal pigmentation/Melasma could also be triggered by these mast cells which cause inflammation. 


Mast cells could be triggered in response to the inflammatory/high histamine foods, sun tanning, sunbeds, steam rooms, saunas, toxins, heavy metals, pesticides, toxic mold, chronic infections (tick bite and viruses), or chemicals resulting in a range of chronic skin conditions. 

Melasma could be a result of cumulative sun exposure and sun damage to the skin. This causes inflammatory cells, particularly mast cells, which play a key role in melanin production  

Mast cells are more frequently observed in the skin of patients that suffer from melasma especially in sun-damaged areas such as the face, sides of the neck, and forearms i.e. all the areas that are chronically sun exposed. The release of histamine in the human dermal mast cells is upregulated in a response to UV irradiation.  

In a clinical study that used special staining, the number of dermal mast cells was significantly higher in lesional melasma skin than in normal skin. 

  • Histamine stimulates the proliferation and migration of melanocytes and stimulates melanogenesis. Thus, mast cells may initiate epidermal pigmentation, which is the main feature of melasma. 
  • Several studies have shown that the number of mast cells is significantly increased in sun-damaged skin.
  • Repetitive UV irradiation also promotes the production of mast cell TRYPTASE, which has been demonstrated to be involved in dermal ECM (substance) degradation.  
  • Mast cell tryptase degrades type IV collagen.
  • Thus, elevated mast cell numbers and tryptase levels could weaken the basement membrane in melasma skin which causes melanin to be deposited into the dermis.
  • Mast cell tryptase could also trigger solar elastosis (excessive, hard, abnormal collagen). 
  • By inducing the production of elastin by fibroblasts, either directly or via other cell types or cytokines.
  • Finally, mast cells can also induce vascular proliferation by secreting small blood vessel forming factors.

Emotional stress is associated with the activation of a variety of neuro-immune-endocrine systems. Numerous other factors are activated in stress, such as α-MSH, (Melanocyte Stimulating Hormone ) which increases and causes pigmentation   

MCAS can cause, worsen or trigger a number of issues, including:

  • Eczema
  • Dermatitis
  • Melasma
  • Rosacea
  • Urticaria
  • Pruritis (Itching)
  • Psoriasis
  • Gut problems (bloating, reflux, IBS) 
  • Insomnia (high histamine levels awakens one from sleep at approx. 3 am)  
  • Any condition ending in “itis” eg. osteoarthr “itis” could be due to MCAS  
  • Allergies and reactions to foods due to Histamine 

Histamines and other types of inflammatory foods which most people think are healthy can actually be making you worse. Unfortunately, foods that may be healthy for a lot of other people can be really bad when you have MCAS. 

One has to figure out how to eat foods that are healing for you and how to spot foods that would make you worse. By making good food choices and getting inflammation way down, skin conditions, itching, sleep issues, and leaky gut can improve once MCAS is under control.

See our webpage on Histamine

Sharon Izak Elaine Chat staff ) WhatsApp
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