The Case:  Rachel is dealing with digestion problems, sleep issues, headaches, psoriasis, and rashes.  She’s seen a ton of specialists, including a dermatologist, gastroenterologist, neurologist, and an endocrinologist She tried steroids, acid lowering medications, and a Selective Serotonin Reuptake Inhibitor (SSRI) with little improvement.   The Investigation This battery of symptoms may seem unrelated but I suspected that they were all connected.  My first clue was in her diet - which was not unhealthy but did have one common element that raised my suspicions. It’s found naturally in many foods and many traditional doctors don’t know to look for it - despite the fact that it’s estimated that as much as 17% of the population may have a reaction to it.  Dr. Beth O’Hara is a Functional Naturopath and the owner of Mast Cell 360, a Functional practice specializing in root cause approach to Mast Cell Activation Syndrome, Histamine Intolerance, and related conditions such as oxalates, mold toxicity, and chemical sensitivities.  You may recall that Beth appeared on episode 67 when we discussed a case involving oxalates.  This time we’re focusing on mast cell activation syndrome and histamine intolerance, which I suspected in Rachel’s case.    What is Histamine Intolerance? Most people think of allergies when they think about histamines because antihistamines are taken to deal with the symptoms. However, histamine has a much bigger role in the body than reacting to allergens. Histamine helps regulate estrogen levels, the sleep-wake cycle, acts as neurotransmitter, activates stomach acid and plays a role in digestion. The body can build up high levels of histamines to a point where the enzymes that break down histamine can’t keep up. At this point, it exceeds the threshold causing a histamine intolerance that leads to many different symptoms.    Symptoms of Histamine Intolerance There are a wide range of symptoms and they vary from person to person. Here are the big ones:   Skin irritation Rashes or hives Headaches (even migraines)  Gastro-intestinal issues Inflammation   Causes of Histamine Intolerance There are many things that can push histamine levels over the top including environmental toxins and certain foods. Some of the most common foods that are high in histamines include:  Spinach Strawberries Pineapple Fish (especially tinned) Packaged/processed foods   Click here for a comprehensive list of high and low histamine foods.  In addition to diet and environmental triggers, there are also genetic factors to consider. Specifically the genes that are coded for histamine degrading enzymes like ABP1 and AOC1 that produce diamine oxidase (DAO). Also, Histamine N-Methyltransferase (HNMT) which is another gene with the function of breaking down histamines.  Alternatively, a gut issue where the microbiome is impeding the natural creation of DAO can also cause a histamine overload.    What is Mast Cell Activation Syndrome Sometimes a histamine intolerance is caused by mast cell activation. Mast cells are the frontline defenders of the immune system and they produce histamine. These cells are activated when there is a threat like a virus, bacteria, parasites, mold or toxins. When they find this issue, they surround it with inflammation producing molecules and call to other immune cells to come in and do the rest of the clean-up process. This activation can result in an over-production of histamine. If the body is under constant attack (from toxins or stress), then mast cell activation can turn into mast cell activation syndrome. This can manifest in many ways with a variety of symptoms and can be difficult to diagnose.    Testing for Histamine Intolerance and Mast Cell Activation Syndrome Diagnosing mast cell activation syndrome is to see if there are symptoms involving two or more systems of the body. For example, GI issues, headaches, hives or others listed here. One of the first diagnostic tests is to have the patient take an