HF 8114

Mast Cell Activation Syndrome and Diet

Mast Cell Activation Syndrome (MCAS)

MCAS is a syndrome with symptoms related to overactive mast cells. Mast cells are part of your immune system. They are found in most parts of your body especially your skin and intestines. They protect you by making chemicals like histamine when a foreign substance enters your body. In MCAS, mast cells are triggered when a harmless substance enters your body and causes a reaction.


Symptoms in two or more organs in your body.


  • Hives

  • Swelling under the skin

  • Skin flushing

  • Itchy skin

  • Red eyes


  • Nausea

  • Vomiting

  • Diarrhea

  • Belly cramping


  • Fainting

  • Fast heart rate


  • Wheezing

  • Hoarseness

  • Nasal congestion

  • Headache

You have a positive test of MCAS that is done while you are having symptoms.

You have a clear decrease in symptoms while on medicines that target MCAS.

Nutrition can be Part of Treatment

Certain foods may trigger your symptoms. You can’t eat the same amount of food you used to. You may have unwanted weight loss and poor nutrition. A dietitian can help you:

  • Eat a balanced diet.

  • Maintain a healthy weight.

  • Fix problems with vitamin and mineral levels.

Special Diets for MCAS

Current guidelines do not suggest any special diet for people with MCAS. However, reducing the histamine in your diet may help.

A Low Histamine Diet

Your provider may suggest a histamine gentle diet that may improve symptoms. This diet reduces foods that are known to be higher in histamine. These include:

  • Avocado

  • Citrus

  • Dried Fruit

  • Tomatoes

  • Spinach

  • Canned or smoked fish

  • Aged/hard cheese

  • Alcohol

  • Eggs

  • Nuts

  • Cured meats

  • Chocolate

  • Leftovers (especially ones with meat)

Your provider may also suggest ways to prepare food that will not promote histamine, such as baking, boiling or air frying.

It is still not known if following a low histamine diet will help if you have MCAS. You may not feel better after taking these foods out of your diet.

We suggest you work with a dietitian to find safe foods to eat as part of a balanced diet.

  • A variety of foods such as meats, fish, eggs, vegetables, fruits, grains, dairy, and oils.

  • Enough calories to support a healthy weight.

  • Limited added sugar, trans fat, saturated fat, and salt.


Other Nutrition Tips

  • Avoid diets that take many foods out of your diet to see if your symptoms improve.

  • Follow the “Rule of Threes”

    • Eat 3 meals a day and up to 3 snacks.

    • Eat at least every 3 hours.

    • Eat at least 3 food groups at each meal.

  • If you are not able to eat enough, you may need a multivitamin.

  • Liquid nutrition shakes may help if you need more calories. (Boost®, Ensure®, and Orgain®).

  • If you feel limited in what you can eat, a dietitian can help you choose the best foods to add back into your diet at your own pace.


Who to Call

If you are a UW Health patient and have more questions, please contact UW Health at one of the phone numbers listed below. You can also visit our website at https://www.uwhealth.org/nutrition

Nutrition clinics for UW Hospital and Clinics (UWHC) and American Family Children’s Hospital (AFCH) can be reached: (608) 890-5500.