Chemical Intolerance, Mast Cells, and Histamine: What’s the Connection?

Are you experiencing eczema, congestion, sinus issues, coughing, frequent headaches and migraines, fatigue, brain fog, joint and muscle pain, digestive issues, or mood changes? Are you still using conventional products filled with chemicals and toxins? You may have chemical intolerance.

Chemical intolerance (CI) or multiple chemical sensitivity (MCS) is a chronic and complex health condition characterized by widespread symptoms related to chemical exposure, often at a level that is seemingly not problematic for most people. Chemical intolerance can lead to physical, psychological, emotional, social, and economic consequences. It can disrupt and limit your daily life, job performance, school work, family life, social activities, and mental health. It may even lead to disability.

So I just have to remove all chemicals from my life, right?! It’s not that simple. You have to look at the root cause of your issues. While chemicals trigger your symptoms, you have to understand the mechanism behind chemical intolerance to address the real problem. New research has found that your mast cells may play a role in chemical intolerance. Today, I want to talk about the connection between chemical intolerance and mast cell activation, and how to address them.

In this article, you will learn about chemical intolerance. You will learn what chemical intolerance is, what are the symptoms of chemical intolerance, and what triggers it. You will learn about mast cell activation syndrome (MCAS) and histamine intolerance. You will understand their symptoms and what’s the difference between the two. Then I will discuss the connection between chemical intolerance, mast cells, and histamine. Finally, I will offer some strategies to address chemical intolerance and MCAS and regain your health and well-being naturally.

What Is Chemical Intolerance?

Our world is full of chemicals and toxins. And they are not good for us. Coming in contact with chemicals through touch, air, food, or water, can have detrimental health effects. Though you may not notice any issues right away, long-term or high exposure to certain chemicals and toxins can lead to a variety of health issues, including allergies, asthma, birth defects, infant brain development issues, reproductive issues, obesity, cardiovascular disease, cancer, diabetes, and behavioral health issues (1).

These are serious enough issues to make you feel concerned. But what if, on top of these long-term health risks, chemical exposure makes your day-to-day life intolerable?
Most of us don’t experience serious immediate reactions to chemicals. Some of us are allergic or sensitive to a few things. But some people have a serious issue with chemical exposure due to chemical intolerance. 

Chemical intolerance (CI) is often referred to as multiple chemical sensitivity (MCS). It is a chronic health condition characterized by a long list of complex chronic, recurring, and possibly severe symptoms due to low-level chemical exposure. When I say low-level exposure, I mean a level that is seemingly unproblematic for most of the population (at least in the short run) (2, 3, 4). 

Symptoms of chemical intolerance can affect various tissues and multiple organs across your body. This also means that symptoms of chemical intolerance can be widespread. You may experience symptoms that are seemingly unrelated or that you can’t explain.

Chemical intolerance can lead to physical, psychological, emotional, social, and economic consequences. It’s not unusual for symptoms of chemical intolerance to become so problematic to seriously affect or limit your daily life, school work, job performance, family life, social life, and mental health. In the most severe cases, chemical intolerance may lead to disability and other serious health issues. 

Symptoms of Chemical Intolerance

Chemical intolerance can affect multiple organs across your body and can lead to widespread symptoms. You may notice that symptoms of chemical intolerance can resemble or overlap with symptoms of histamine intolerance or mast cell activation syndrome (MCAS). I will get into the connection between chemical intolerance, mast cells, and histamine later. But first, let’s look at the symptoms of chemical intolerance.

If you have chemical intolerance, you may experience any or all of the following symptoms:

  • Headaches or migraines
  • Rashes, eczema, or other skin problems
  • Congestion, runny nose, sore throat, coughing, sinus pain, or other respiratory symptoms
  • Dry, sore, or watery eyes
  • Ear aches
  • Symptoms of asthma
  • Breathing problems, including chest pain and coughing
  • Brain fog 
  • Confusion, memory problems, trouble concentrating
  • Fatigue and sleep issues
  • Muscle aches and pain
  • Joint pain or stiffness
  • Bloating, gas, diarrhea, constipation, abdominal pain, or other digestive issues
  • Changes in heart rhythm
  • Mood changes
  • Mental health symptoms, including anxiety, depression, and hyperactivity

Triggers of Chemical Intolerance

There are so many chemicals in our world. You may not be surprised that a long list of chemicals can trigger chemical intolerance. 

Potential triggers of chemical intolerance may include but are not limited to the following:

  • Auto fuel and exhaust
  • Tobacco smoke
  • Smoke from a wood-burning stove
  • Forrest fire and volcano ash
  • Asphalt pavement
  • Chlorine
  • Body wash
  • Shampoo
  • Soaps 
  • Perfumes or cologne
  • Aftershave
  • Deodorant
  • Hair spray
  • Nail polish and nail polish remover
  • Makeup
  • Other conventional personal hygiene, body, and beauty products
  • Varnish
  • Tile cleaner
  • Window cleaner
  • Toilet cleaner
  • Bleach
  • Drain cleaners
  • Other conventional cleaning products
  • Paint
  • Plastics
  • New carpet
  • Air fresheners
  • Restroom deodorizers
  • Insecticide
  • Pesticides
  • Herbicides
  • Food additives
  • Plastics
  • Markers

Mast Cells and Histamine

As you’ve noticed, symptoms of chemical intolerance can be similar to symptoms of MCAS and/or histamine intolerance. There is a good reason for that. Your mast cells play a role in chemical intolerance. I see many patients with histamine intolerance and MCAS who also struggle with chemical intolerance. But before I get into the connection between chemical intolerance and your mast cells, I want you to understand some terms around mast cells and histamine.

What Is Mast Cell Activation Syndrome

Your mast cells are white blood cells found in your digestive tract, respiratory tracts, skin, reproductive organs, surrounding nerves, and blood. They store inflammatory mediators, including histamine, which means that they play an essential role in your immune health and immune response. When your body encounters allergens, toxins, or other foreign invaders, your mast cells will trigger an allergic response. This allergic response triggers the release of histamine and other chemicals to protect your body.

This mast cell activation is there as a protective mechanism to help fight allergens and foreign invaders. However, overactivation of your mast cells and other mast cell activation issues can become a problem. 

Mast cell activation syndrome (MCAS) is a complex health issue. It involves and affects a number of different systems in your body. By affecting so many parts of your body, it can lead to a variety of widespread symptoms (5, 6, 7, 8).

Symptoms of MCAS

Symptoms of MCAS will impact more than one part or system of your body. Symptoms may vary from person to person. They may be anywhere from mild to severe. Symptoms of MCAS may include:


  • Rashes
  • Hives
  • Itching
  • Heart palpitations
  • Low blood pressure
  • Headaches
  • Chest pain
  • Weight changes, including rapid weight loss or weight gain
  • Digestive trouble, including diarrhea, nausea, and vomiting
  • Loss of appetite or low appetite
  • Anxiety
  • Fatigue
  • Vision changes
  • Weakness
  • Dizziness

Triggers of MCAS

Triggers of mast cell activation may include:

  • Allergens
  • Mold
  • Toxins
  • Heavy metals
  • Chemicals
  • Medications
  • Infections
  • Viruses
  • Food 
  • Alcohol
  • Physical and psychological stress

Common Causes of MCAS

There are 3 types of MCAS (12, 13):

  • Primary MCAS: Primary MCAS may develop due to a genetic mutation called the KIT D816V mutation. People with this type of MCAS often have mastocytosis, which means that your body is making too many mast cells. Mastocytosis is a very rare condition.
  • Secondary MCAS: Secondary MCAS may develop because of an IgE-mediated food or environmental allergen, another immunologic problem, or hypersensitivity to a trigger.
  • Idiopathic MCAS: Idiopathic MCAS is a term used when the exact cause of MCAS is unclear or cannot be determined.

What Is Histamine Intolerance

Histamine is a chemical produced by your body, which plays an essential role in your immune health and other areas of your body. Most people have only heard about histamine from taking antihistamines for allergies. The anti part of antihistamines can be confusing. Many people think that histamine is bad when in fact, histamine is critical for your health and well-being.

Histamine helps your body to get rid of allergens. It also supports your digestion by releasing hydrochloric acid to break down food and bacteria. It serves an essential role in your brain health by serving as a chemical messenger between your brain and the rest of your body.

Even though histamine is necessary for your health, you don’t want too much of it. Too much histamine can turn into a serious problem. f your body is releasing too much histamine, but it’s unable to break down all the excess histamine, histamine build-up occurs. 

Histamine intolerance means that there is too much histamine in your body. In a healthy body, there are enzymes, including the DAO enzyme, to break down excess histamine and prevent build-up. But if you have too much histamine due to high-histamine foods, mast cell activation issues, the lack of DAO enzyme, stress, or other reasons, your body won’t be able to break everything down. This can lead to histamine intolerance. 

Histamine intolerance means that your body has too much histamine. Histamine intolerance can affect your entire body, including your gut, brain, lungs, and cardiovascular system. Because histamine intolerance can affect your entire body, it can cause widespread symptoms that don’t seem to connect at first glance (9).

Symptoms of Histamine Intolerance

Symptoms of histamine intolerance may include:

  • Headaches and migraines
  • Fatigue
  • Congestion and runny nose
  • Hives
  • Rashes, eczema, psoriasis, and other skin symptoms
  • Asthma attacks
  • Crawling skin sensation on skin or scalp
  • Flushing
  • Diarrhea and other digestive issues
  • Low blood pressure
  • Hypertension
  • Racing heart rate
  • Dizziness or vertigo
  • Abnormal menstrual cycle and premenstrual syndrome (PMS)
  • Sleep issues
  • Brain fog and forgetfulness
  • Irritability and mood imbalances
  • Anxiety or panic attacks

Are MCAS and Histamine Intolerance the Same?

Though the symptoms of MCAS and histamine intolerance can be similar and may overlap, they are not the same. Having histamine intolerance means that your body has a histamine build-up from high-histamine foods, environmental toxins, stress, and other histamine-promoting factors that your body is unable to handle and break down effectively. Having MCAS means that your mast cells get triggered and activated by allergens, mold, toxins, chemicals, medications, infections, stress, pain, or other triggers leading to an immune response and histamine release.

MCAS and histamine intolerance can co-occur. MCAS can also cause histamine intolerance. In fact, I’ve found that MCAS is one of the most common driving factors for histamine intolerance. I personally have MCAS and had histamine intolerance as a result. I see patients all the time with both MCAS and histamine intolerance. 

However, you can develop histamine intolerance without MCAS. You may also have MCAS without symptoms of histamine intolerance. Though you may have both conditions, it is absolutely possible only to have one.

The Link Between Mast Cells and Chemical Intolerance

Now that you understand how your mast cells and histamine work, it’s time to discuss the connection between chemical intolerance and your mast cells. A 1996 research paper published in Toxicology has discussed how chemical intolerance develops (10). Claudia Miller, MD, a tenured professor at the Occupational and Family Medicine department at the University of Texas and author of this paper, has explained that chemical intolerance is a two-stage disease process. This two-stage process is called toxicant-induced loss of tolerance (TILT). 

Chemical intolerance first begins with exposure to chemicals. This can be one acute serious exposure or a series of lower-level exposure. A series of low-level is a more common experience for most people. This chemical exposure can cause a loss of tolerance to the chemicals and result in the multi-system symptoms of chemical intolerance.

You may develop chemical intolerance if you have never had a reaction to chemicals or toxins before. In fact, chemical intolerance most commonly develops after repeated low-level chemical exposure or one specific, acute, serious chemical exposure in people who never had an issue with chemicals before. 

Practitioners and researchers have connected chemical intolerance to allergies and chemical toxicities. However, until a more recent study, we didn’t have a good understanding of the mechanism of chemical intolerance. A 2021 study published in Environmental Sciences Europe has found that there may be a link between chemical intolerance and mast cell activation, explaining the potential problem behind your symptoms.

Researchers used the Quick Environmental Exposure and Sensitivity Inventory (QEESI). This is a 50-question validated questionnaire and international reference standard used for chemical intolerance screening and diagnosis by both researchers and clinicians. It may also be useful as a self-assessment tool. For this study, researchers use the QUEESI to uncover the connection between chemical intolerance and mast cell activation.

In the study, they looked at 345 patients with reported chemical intolerance, 147 subjects with MCAS, and 76 healthy control participants. Considering how chemicals are one of the main triggers behind MCAS, the results may not be surprising. They found that 59 percent of the patients with MCAS also met the diagnosis criteria for chemical intolerance. Researchers also found that MCAS may increase the likelihood of having chemical intolerance and the risk of developing chemical intolerance in the future. They also noted that the symptoms and characteristics of chemical intolerance and MCAS overlap to a great extent. 

Exposure to chemicals can activate but also play havoc with your mast cells. This may lead to mast cell activation problems, chemical intolerance, or both. Since MCAS is a common driving factor of histamine intolerance, MCAS and MCAS-related chemical intolerance can lead to histamine intolerance as well.

This research is a really important step in the right direction allowing healthcare practitioners to uncover the root issues behind chemical intolerance and MCAS and offer effective solutions for complex health issues and multisystem symptoms. Moreover, it helps to understand the potentially dangerous health effects of environmental toxins and chemicals better.

My Recommendations for Chemical Intolerance, Histamine Intolerance, and MCAS

If you are experiencing symptoms of chemical intolerance, MCAS, and histamine intolerance, I have a few recommendations to improve your health naturally.

Reduce Your Triggers

Avoiding exposure to chemicals is the first step if you have chemical intolerance. Avoiding chemicals, heavy metals, and other environmental toxins is also critical for reducing the risk and symptoms of MCAS. Stop using conventional, chemical-filled cleaning, personal hygiene, body, and beauty products, and any products that you find triggering. Choose organic, natural, and homemade alternatives instead. Reduce the use of plastics as much as possible and choose glass, wood, bamboo, silicone, and organic cotton alternatives instead, depending on the product. Drink purified water instead of tap. Buy a high-quality air filtration system to avoid indoor air toxins. Choose organic food or grow your own organic food to avoid exposure to pesticides, herbicides, hormones, and antibiotics.

Detoxify Your Body and Support Your Liver

Supporting your body to cleanse itself from chemicals, toxins, heavy metals, mold, and other triggers is an important step for recovering from MCAS. Drink plenty of purified water, move your body and use an infrared sauna to support detoxification through sweating. Try dry skin brushing and rebounding to support lymphatic cleaning. Support your gut health through an anti-inflammatory, gut-friendly diet and probiotics to support the digestion and absorption of nutrients and elimination through bowel movements.

Support your liver. Your liver is an important detoxifying organ. However, having too much histamine can cause liver enzyme changes and liver dysfunction compromising your entire health. This is why I recommend you support your liver with a variety of strategies, including castor oil packs, that I go over in my book, The 4-Phase Histamine Reset Plan: Getting to the Root of Migraines, Eczema, Vertigo, Allergies and More. I also recommend a liver-supporting supplement, such as Optimal Reset Liver Love.

Try a Low-Histamine Diet and Reduce Your Histamine Bucket

To improve your health by addressing histamine intolerance, I recommend that you follow a nutrient-dense and low-histamine diet. Remove all histamine foods for one to three months, then slowly re-introduce them one by one following The 4-Phase Histamine Reset Plan. If you want to go a step further, you should join my Histamine Reset Online Program.

Remove inflammatory foods, including refined sugar, refined oils, canned and processed meat, artificial ingredients, junk food, and highly processed foods. Avoid high-histamine foods, such as fermented food (eg. sauerkraut, kimchi, fermented vegetables, kombucha, etc), aged food (eg. aged cheese, processed meat, canned fish, etc), over-ripe fruits and vegetables, leftovers, and foods that are naturally high in histamine (eg. avocadoes, eggplant, spinach, dried fruits, etc). Avoid foods that may trigger histamine releases, such as tomatoes, most citrus, bananas, most nuts, and dairy. Avoid foods that may block the DAO-enzyme, including black tea, green tea, alcohol, and energy drinks.

Eat a nutrient-dense, anti-inflammatory, and low-histamine diet rich in greens, vegetables, herbs, spices, fruits, healthy fats, and organic meat. Low-histamine foods include most fresh leafy greens and vegetables, non-citrus fruits, such apples, pear, papaya, and grapes, fresh grass-fed meat, pasture-raised poultry and eggs, and wild-caught fish, olives, extra-virgin olive oil, ghee, coconut oil, leafy herbs, and herbal tea. My book, The 4-Phase Histamine Reset Plan includes an extensive list of foods that you can eat and should avoid on a low-histamine diet.

 In addition to these recipes, I recommend all the low-histamine recipes in my other two low histamine cookbooks,  Low Histamine Cooking in Your Instant Pot and Fifty One Low Histamine Air Fryer Recipes. They are all simple, easy to make, low-histamine, gluten-free, Paleo-friendly, and super healthy.  The instant pot and air fryer are amazing tools to help cook food quickly so that it does not release a lot of histamine. The longer you cook food, the more histamine it releases.

Additionally, improve your lifestyle to reduce your histamine bucket. Stress, poor sleep, environmental toxins, and other poor lifestyle habits can increase histamine intolerance. I’ve already covered the importance of reducing your toxin load. Additionally, I recommend that you reduce your stress levels, improve your sleep, and move your body regularly. 

To reduce stress, I recommend meditation and breathwork. Get 7 to 9 hours of sleep each night. Move your body and stretch regularly, and exercise at least 5 days a week. I highly recommend resistance training if possible and aiming for about 10K steps in each day.

Try Neural Retraining

You may develop chemical intolerance due to an imbalance in your limbic system. Your limbic system refers to a part of your brain that affects your behavioral and emotional responses. It plays a role in feeding, reproduction, caring for our children, and the fight-or-flight response. Toxins, infections, physical or psychological trauma, stress, inflammation, and other issues can create a limbic imbalance and related health issues, including chemical intolerance. Repeated low-level chemical exposure or acute high-level chemical exposure can create condition trauma in your amygdala, insula, and your limbic system leading to a conditioned limbic system response causing your symptoms. 

Fortunately, you can retrain your limbic system using the principle of neuroplasticity. Neuroplasticity helps to change your brain and create new neural networks to recreate homeostasis, safety, health, and well-being. Though this is a relatively new field without enough research evidence, plenty of anecdotal evidence suggests that it works. If you are interested in limbic retraining, I highly recommend the Gupta Program™ Brain Training. We also interviewed Ashok Gupta, the creator of this program, on our Health Babes podcast. You can watch it here or listen to it here to learn more about your limbic system and retraining your brain.

Final Thoughts

Chemical intolerance is a chronic and complex health condition characterized by widespread symptoms, including eczema, congestion, sinus issues, coughing, frequent headaches and migraines, fatigue, brain fog, joint and muscle pain, digestive issues, or mood changes, related to chemical exposure, often at a level that is seemingly not problematic for most people. Chemical intolerance can seriously disrupt your physical, psychological, emotional, social, and economic well-being and may even lead to disability. 

Research suggests that your mast cells may play a role in chemical intolerance. This means that you have to address underlying mast cell activation issues and histamine intolerance to address and recover from chemical intolerance and its symptoms effectively. I recommend that you follow my tips to repair your body from chemical intolerance and MCAS. Since chemical intolerance, MCAS, and histamine intolerance are complex health issues with a list of potential underlying issues, you may benefit from scheduling a consultation with a functional medicine practitioner (hint: us!).

If you are dealing with chemical intolerance, MCAS, or histamine intolerance, I invite you to schedule a consultation with us. We can help identify the root cause of your condition and recommend a personalized treatment plan to repair your body and regain your health and well-being. Schedule your consultation here.

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Hi, I am Dr. Becky Campbell. I work with men and women who’ve had a health set back and are willing to do whatever it takes to reach optimal health so they can perform their best in their careers and be fully present with their family again.

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