Histamine Reaction: What It ACTUALLY Looks Like Inside and Out

by | Sep 7, 2023 | Blog, Histamine

Redness. Swelling. Itching. Sneezing. 

These are all possible signs of a histamine reaction. But why are you having a histamine reaction? And what can you do about it? 

This is exactly what I want to talk about today. There may be a number of reasons why you are having a histamine reaction. You may have one trigger, or you may have a laundry list of underlying reasons. The root cause behind your issue may trigger a histamine reaction here and there, or it may cause you to deal with chronic symptoms of an ongoing histamine reaction.

Understanding the underlying root cause of a histamine reaction is essential for reducing your risks and improving your symptoms. So let’s get into it: what is a histamine reaction and what to do about it!

What Is Histamine

Histamine is a chemical that helps to support your immune system by getting rid of allergens. To protect your body from an allergen, your immune system releases histamine and other chemicals, which then, depending on the type of allergen, may act on various areas of your body, including your nose, throat, lungs, eyes, skin, or digestive tract, causing symptoms of allergy. 

Besides protecting your body from foreign substances, histamine also supports your gut health and digestion by releasing hydrochloric acid. It acts as a neurotransmitter between your brain and other parts of your body, supporting your mental and brain health. 

Histamine is clearly an important chemical. But you don’t want too much of it either. Having too many chemicals or histamine intolerance can cause a chronic histamine response and chronic symptoms. Understanding whether you are dealing with a histamine reaction from allergies or histamine intolerance can help you come up with a plan to reduce histamine reactions and symptoms in the first place.

What Is the Difference Between Allergies and Histamine Intolerance?

Histamine helps to fight allergies. If you come in contact with an allergen, whether that’s seasonal allergies, dust mites, pet fur, mold, or food allergens, you will experience a histamine reaction. This may lead to similar symptoms to histamine intolerance, including redness, itching, skin rashes, runny nose, sneezing, coughing, watery eyes, or tummy troubles. 

Since symptoms of allergies and histamine intolerance can be very similar and both have to do with histamine, distinguishing between the two can be difficult at first glance. However, allergies and histamine intolerance are not the same: their triggers and underlying mechanisms are different.

An allergy is a reaction from your immune system to a substance, such as pollen, animal dander, dust, or food. On the other hand, histamine intolerance refers to a build-up of histamine in the body.

What Are Allergies?

Allergies develop when your immune system revolts against and reacts to a foreign substance, such as pollen, pet dander, insect venom, mold, dust, or food. These reactions occur to substances that many or most people don’t have problems with, yet, some people do. Some allergies are more common than others. For example, about a quarter of the US population has some form of a seasonal allergy, while only about 6% has true food allergies (1). 

If you have allergies, your immune system makes something called antibodies. Antibodies are substances that identify certain substances as harmful. When you come in contact with an allergen your body identified as harmful, your body will proceed to create an antibody called immunoglobulin E (IgE). IgE will trigger the release of histamine and other chemicals, which will lead to allergic reactions and symptoms. 

In many cases, for example, with seasonal allergies, symptoms may be mild. However, in other cases, it may result in anaphylaxis, which is a life-threatening emergency. 

Symptoms of Allergies

Symptoms of allergies may depend on the type of allergy:

  • Symptoms of hayfever and seasonal allergies may include: 
      • Sneezing
      • Runny nose
      • Stuffy nose
      • Itchy eyes or nose
      • Red, watery, or swollen eyes
      • Coughing
  • Symptoms of food allergies may include:
      • Hives
      • Swelling of the lips, tongue, throat, or face
      • Tingling in the mouth
      • Anaphylaxis
  • Symptoms of insect bite allergies may include:
      • Itching or hives all over the body
      • Large area of swelling
      • Redness
      • Pain 
      • Coughing, wheezing, chest tightness, or shortness of breath
      • Anaphylaxis
  • Symptoms of drug allergies may include:
      • Hives
      • Rashes
      • Redness
      • Itchy skin
      • Wheezing
      • Facial swelling
      • Anaphylaxis
  • Symptoms of allergic skin reactions (atopic dermatitis) may include:
    • Redness
    • Swelling
    • Itching
    • Flaking
    • Peeling

What Is Histamine Intolerance

Histamine is essential for your health and wellness. However, too much histamine can turn into a serious problem. Too many high-histamine foods, environmental toxins, stress, and other factors can lead to too much histamine and an increased release of histamine in your body. If your body has too much histamine and is unable to deal with it, it will lead to histamine buildup. This histamine buildup, called histamine intolerance, can affect your entire body and cause widespread symptoms.

Symptoms of Histamine Intolerance

Symptoms of histamine intolerance may be widespread and seemingly separate from each other. They may be anywhere from mild to severe.

Symptoms of histamine intolerance may include:

  • Headaches and migraines
  • Eczema, dermatitis, acne, and other skin issues
  • Hives
  • Fatigue and sleep issues
  • Red eyes
  • Dizziness or vertigo
  • Heart palpitation or racing heart
  • Brain fog, confusion, memory issues
  • Irritability and mood swings
  • Anxiety or panic attacks
  • Allergies 
  • Asthma
  • Congestion or runny nose
  • Acid reflux, bloating, diarrhea, and other digestive symptoms
  • Abnormal menstrual cycle and premenstrual syndrome (PMS)

How to Distinguish Between Allergy and Histamine Intolerance

Identifying your triggers and looking at the underlying mechanisms behind your symptoms can help you identify whether you have an allergy or histamine intolerance. Allergy testing is a great option. If you are dealing with reactions to food, a food journal, and elimination diet may be a great option too. If the underlying cause is histamine intolerance, a low-histamine diet, and lifestyle changes should help with your symptoms.

The Root Cause of Histamine Reactions

Without understanding the root cause of any health issue, you can’t address it properly and recover completely. There may be a number of underlying issues and triggers that may lead to a histamine reaction. Some of the main root causes of a histamine reaction include:

    • Allergies: One of the most common causes of histamine reactions is allergies. Your immune system wants to protect you from perceived harm, often to substances that are not threatening to the entire population (2).
    • Inflammation: A histamine reaction plays a critical role in early acute inflammatory response. Your body may release histamine when you are experiencing an infection, injury, or other trauma. This histamine reaction aims to remove products of cell damage from inflammation (3).
    • Histamine intolerance: You develop histamine intolerance when a build-up of excess histamine occurs in your body caused by a high-histamine diet, chronic stress, environmental toxins, a deficiency in the diamine oxidase (DAO) enzyme, and other factors. Histamine intolerance may lead to a constant histamine reaction and related chronic symptoms (4).
    • High-histamine foods: Certain foods are naturally high in histamine. Other foods are histamine-liberating, which means that they trigger histamine release. Eating too much of these foods may fill up your bucket, increase histamine intolerance, and trigger a histamine reaction (5).
    • Gut microbiome imbalance: Your gut affects your entire body. If your gut microbiome is out of balance, it may disrupt your body’s ability to break down histamine efficiently. This may increase histamine levels and histamine reactions (6).
    • Environmental toxins: Environmental toxins, including chemicals, heavy metals, and mold, may increase mast cell activation and trigger your immune system to release histamine. Even without an allergy to these substances, you may experience a histamine reaction to a variety of environmental triggers (7).
    • Stress: Both emotional and physical stress may trigger a histamine reaction. Chronic emotional stress or physical stress may contribute to histamine intolerance. They are also a risk factor for mast cell activation issues and related histamine release (8).
    • Medications: Certain medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) and antibiotics, may increase histamine release or may compromise your ability to break down histamine. Certain medications may also increase mast cell activation and related histamine reactions (9).
    • Methylation deficiency: Methylation plays a role in the breaking down of histamine. Methylation deficiency due to an MTHFR gene mutation or certain nutrient deficiencies (e.g., vitamin B6, B12, and folate) may reduce the clearance of histamine, increasing histamine intolerance and histamine reactions (10).
  • DAO or HNMT genetic variations: DAO and HNMT are enzymes directly involved in the breakdown of histamine. If not produced in adequate amounts, histamine can be allowed to build in your body due to deficiencies in these key enzymes. Why might they not be produced in adequate amounts? This can occur due to variations in the genes you were born with that code for the making of these enzymes. As we age, enzymes become less efficient also, in addition to any genetic predispositions.


Identifying the causes and triggers of your histamine reactions on your own can be tough. I recommend working with a doctor who is well-versed in issues related to allergies, histamine intolerance, and mast cell activation.

How to Manage Your Histamine Reaction

Now you understand what a histamine reaction looks like. It’s time to reduce your risks and improve histamine reactions. Here is what I recommend. 

Follow a Low-Histamine Diet

You may benefit from following a low-histamine diet for 3 to 4 weeks with plenty of anti-inflammatory, nutrient-dense, low-histamine foods. Avoid inflammatory foods, such as refined sugar, refined oil, artificial ingredients, gluten, heavily processed foods, and junk food. Avoid high-histamine foods that can trigger histamine release, or may act as diamine oxidase or DAO enzyme blockers, and increase histamine levels as described in this article.

 Reduce acidic foods that may be triggering interstitial cystitis and bladder pain, including chili, spicy foods, green apples, pineapple, nectarines, peaches, tomatoes, tea, and vinegar (11). Eat plenty of low-histamine, anti-inflammatory, nutrient-dense whole foods, such as greens, vegetables, herbs, fruits, eggs, pasture-raised poultry, grass-fed beef, and wild-caught fresh fish. For patients in my clinical practice, this diet change on its own has oftentimes resulted in marked improvement in symptoms. 

Reduce Your Histamine Bucket

Following a low-histamine diet may not be enough to reduce your symptoms. You have to reduce your histamine bucket by paying attention to other lifestyle and environmental factors. Avoid medications, chemicals, environmental toxins, heavy metals, and other irritants that may trigger mast cell activation. It is particularly important to be mindful of any chemicals that come in contact with the local area, including clothing. Reduce your stress and anxiety. Exercise and move your body regularly. Improve your sleep. 

If you are currently experiencing a histamine reaction, try not to stress. Remember, stress itself may increase inflammation, histamine release, and histamine reactions. Reach into your toolbox to reduce your stress and get some sleep to encourage healing.

Try Quercetin

Quercetin is a powerful flavonoid that’s found in a number of plants, including blueberries, cranberries, cherries, grapes, black currant, black plums, pepper, cruciferous vegetables, cabbage, romaine lettuce, kale, asparagus, snap pea, sprouts, olive oil, and various herbs. One of the major benefits of quercetin is its ability to lower histamine and allergic responses. You may benefit from eating quercetin-rich foods and taking a quercetin supplement (12).

Try Mast Cell-Stabilizing Foods and Supplements

Try foods that may help to stabilize your mast cells, including watercress, moringa, chamomile, Thai ginger, apples, Brazil nuts, peaches, nettle, onion, fiber-rich foods, and quercetin-rich foods (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24). You may try supplementation with natural antihistamines and mast cell stabilizers, such as quercetin, resveratrol, curcumin, vitamin C, nettle leaf, and luteolin. DAO enzyme may be helpful (25, 26, 27, 28, 29, 30, 31).

Improve Your DAO Enzyme Levels

DAO enzymes help to break down histamine in your body. If your body is not producing enough DAO enzymes, it won’t be able to break down excess histamine, increasing the risk of histamine intolerance and histamine reactions. 

Certain vitamins and minerals, including vitamin B6, vitamin C, zinc, and copper, play a role in the production and function of DAO enzymes. Deficiencies in these micronutrients may increase the risk of low levels of DAO enzymes. On the other hand, getting enough of the micronutrients through food and supplementation may help to improve your DAO enzyme levels and functions.

Since DAO enzymes are mainly made in your small intestines, improving your gut health is also critical for supporting DAO enzyme levels and functions (32).

Try Some Strategies for Immediate Relief

Cool compresses and cool baths may help to deal with skin-related histamine reactions, such as inflammation, itching, swelling, redness, and pain from insect bites or allergic skin reactions. Oatmeal, baking soda, and aloe vera are among the few great options for insect-bite-related histamine reactions. Oatmeal baths and creams are also great for eczema (33, 34). 

Saline nasal irrigation may be a great option for improving symptoms of seasonal allergies. Using indoor air filtration and dehumidifiers may help to reduce indoor allergens and related symptoms. You may also find success with acupuncture (35, 36).

Next Steps

If you are dealing with allergies, histamine intolerance, or mast cell activation syndrome, I recommend that you speak with your doctors first for more personalized health information and support. I invite you to schedule a consultation with me here to see if you can benefit from the strategies listed in this article. 

If you are dealing with any chronic health issues, for advice on how to improve your nutrition and health, I welcome you to start a functional medicine consultation with me for further personalized guidance. You may book your consultation here

Check out my Histamine Intolerance Course here. Learn on your own time, from anywhere. Get an inside look at the most helpful functional medicine tests for pinpointing imbalances, ways to identify and manage the most common (and sometimes surprising) mast cell triggers, and learn what to eat, what to avoid, and why.


Learn more about working with Dr. Gannage