MCAD: General information for public

Mast Cell Activation Disorders (MCAD): Frequently Asked Questions

What are mast cell activation disorders?

They are a group of conditions  in which the mast cells in the body do not function correctly.  MCAD includes systemic mastocytosis, urticaria pigmentosa and mast cell activation syndrome, among other conditions. Mast cells are responsible for allergic responses. In MCAD, patients can have allergic type reactions to things they are not allergic to. These reactions can be very severe and even life threatening.

What are mast cell reactions?

These are reactions caused by mast cells being improperly activated. These reactions vary from person to person. Symptoms can include, but are not limited to, nausea, vomiting, hives, rashes, itching, flushing (turning red), dizziness, confusion and irritability. Symptoms are caused by the chemicals released by the mast cells.

What causes mast cell reactions?

Triggers vary from person to person. More common triggers include heat, cold, friction (especially on the skin), sunlight, foodstuffs, physical exertion, stress, dyes and fragrances. Triggers can also change over time, with new triggers presenting.

Are mast cell reactions dangerous?

YES. Many MCAD patients will experience uncomfortable reactions throughout their lives. However, every reaction carries the risk of anaphylaxis, a life threatening, severe allergic reaction. Therefore, avoiding reactions as much as possible is very important for mast cell patients. Each patient has an individualized response plan. For many, it involves removal of trigger and administration of medication, such as antihistamines or inhalers.

What is anaphylaxis?

Anaphylaxis is a severe allergic reaction affecting multiple organ systems in the body. These are the kinds of reactions observed in patients with bee sting allergies. Anaphylaxis can be fatal. It is a medical emergency requiring immediate treatment, usually epinephrine (Epipen.) Please receive guidance from treating physician on when to use an Epipen.

How are mast cell anaphylaxis and mast cell reactions different from normal allergies (like food allergies?)

With allergies, your body reacts by a specific method that involves ingesting and recognizing the allergen. In MCAD patients, the mast cells incorrectly think many things are allergens. Since mast cells are so sensitive in these people, ingestion of an allergen is NOT necessary to cause mast cell reactions or anaphylaxis. Smelling a perfume or breathing in very hot, humid air is enough to cause a reaction in many MCAD patients.

What causes MCAD?

Genetic mutations cause different kinds of MCAD. Recent studies have shown that mast cell disease can affect multiple members of the same family.

Why do some MCAD patients have spots?

These spots occur in locations where there are more mast cells than usual in the skin. These are NOT contagious rashes. In addition, MCAD patients who do not have permanent spots often have very sensitive skin, which may cause temporary marks or rashes.

How can I help an MCAD patient be safe?

By not being afraid of their disease. Respect their triggers and help them work around these limitations. Reactions can be painful and very scary, especially for kids. Learn the symptoms associated with reactions and be ready to help with a response plan.


Is there more information you feel should be included here?  Let me know in the comments and I can add it in.

23 Responses

  1. Cynthia Easterling October 30, 2014 / 10:04 am

    I would love to see the addition of stress as a trigger. Possibly encouragement for caregivers to understand the stress trigger and attempt to minimize stress in periods of hypersensitivity.

    • Lisa Klimas October 31, 2014 / 12:14 am

      Updated to add physical exertion and stress. Thanks!

  2. Kate Barnwell October 30, 2014 / 10:06 am

    Thank you, Lisa. This is very informative and has some great information. I will definitely share this with my friends and family.

  3. Suzy October 31, 2014 / 1:58 am

    Diarrhea is a big symptom not specifically mentioned. But i know the list of reactions is long though so impossible to list them all.

    • Lisa Klimas October 31, 2014 / 3:49 am

      It is. I actually thought about whether or not to include it here, but chose not to because constipation is also very common and I didn’t want to confuse someone just learning the basics. I am going to be doing a series of “general information” type posts and will do one on symptoms, where diarrhea will definitely be included. Good point. Thanks!

      • dina winkel January 14, 2016 / 2:02 am

        wonder about how one determines if they have MCAD. Certain diagnostic criteria and or tests? Also wonder about chronic daily diarrhea; can this be a symptom?

        • Lisa Klimas January 14, 2016 / 10:01 am

          There are many articles on this site detailing diagnosis. Just search ‘diagnosis’ or click on the tag on the right side of the page.

  4. pete November 2, 2014 / 1:39 pm

    Maybe a link to further symptom breakdown?

    • Lisa Klimas November 3, 2014 / 12:22 am

      Yes. I’m going to do a symptoms post.

  5. Praxia August 3, 2015 / 6:13 am

    Message…Hi, thank you. I have experienced the anaphalactic shock but started now with POTS of which dr’s always try explaining it as Epilepsy !!! . Any more info on this please.

  6. Donna Yavelak August 3, 2015 / 11:55 am

    Please mention that many have weight gain due to physical exercise limitations and medication, plus the disease itself. I get hammered by people all the time and the stress of people on my weight exacerbates my symptoms. I used to be stick thin before my illness started. Also debilitating fatigue. My own family does not believe me as I look fine. Thanks sooo much!

  7. Nicole August 3, 2015 / 1:08 pm

    Have you wrote something like this for systemic mastocytosis?

    • Lisa Klimas August 3, 2015 / 1:17 pm

      MCAD (mast cell activation disease) is an umbrella term that includes both SM and MCAS. This is for both of them.

  8. Kristine October 11, 2015 / 9:11 am

    Thank you for this! I really want to show this to my mom who currently has her head in the sand. All of her offspring have this, she has many symptoms and positive for dermatographia. I was wondering if you would agree to add fever and sore throat, even mouth and throat sores? My sons reactions mimic viruses in most cases. So it was hard to diagnosis in him before we found our specialist.

    • Lisa Klimas October 17, 2015 / 11:10 pm

      Fever is a controversial symptom, there is a lot of disagreement on whether or not it is from MCAD. But yes, I can put it in with a comment that not everyone gets it. The oral sores are becoming more well recognized as part of MCAD, especially since they are often blamed on herpes but biopsy negative.

  9. Praxia October 12, 2015 / 2:29 pm

    Could you please add ore info about POTS.

    • Lisa Klimas October 17, 2015 / 11:08 pm

      I can do a fact sheet about POTS that is separate from this one.

  10. Lisa tweedie November 11, 2015 / 1:27 am

    Thanks for this. I have had Wierd allergic reactions to Neurofen and other NSAIDS. Also to the Mirena coil (hospitalised for 10 days with severe breathing difficulties) possible allergy to progesterone. Nightmare to deal with alongside my EDS and endometriosis. I think this would provide a useful explanation. Can you explain why it would be worth getting a referral to a consultant on this… I need the words to persuade my GP to part with the cash.

  11. Angie Heavner November 11, 2015 / 5:04 pm

    Question about the mast cell plus severe allergic reactions. There was a mention of bee stings and a epipen. Do you know if this may also have any links to malignant hyperthermia? I am asking because I know that bee stings do trigger that reaction in her which I was told was unusual. Alot of unusual allergies and vitamin deffencies plus some rare diagnosis (most are still in the questioning side). Thanks for any info.

    • dina winkel January 14, 2016 / 2:10 am

      Did you find out any answers to your question regarding malignant hyperthermia and mast cell issues? I have serious interest in this given my birth father and brother both died from malignant hyperthermia while undergoing surgical procedures. This was brought on by inability to process general anesthesia from what little i could find out. Certainly is a genetic disorder thats about all i know. Would be very helpful to hear back from you if you have learned anything. Didn’t see any response listed on this site- Thanks!!!!

      • Lisa Klimas January 14, 2016 / 10:00 am

        I’m sorry to hear about your father and brother. I know a child who has mast cell disease and malignant hyperthermia, as well as several other genetic conditions. I am not aware of a direct connection to mast cell disease.

  12. dina winkel January 14, 2016 / 2:07 am

    I also read Angie Heavner posted a question regarding links to malignant hyperthermia and mast cell allergic reactions and epipens for bee stings. My birth father and brother died from malignant hyperthermia while in the hospital for surgery and were administered general anesthesia and went into comas and died. Does anyone know about any connection with Malignant hyperthermia susceptibility and mast cell issues?????????

  13. Kim February 1, 2016 / 4:45 am

    This is a wonderful explanation! Thank you for doing this!

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