Understanding Allergies, Histamine & Food Intolerances

Is it an Allergy, Histamine sensitivity or Intolerance?

Many people suffer obvious, allergy type symptoms, yet have not been tested to determine if its actually an allergy or intolerance, or a histamine clearing issue! Treatment varies with each of these and for those who suffer the symptoms, which is usually for years,  it becomes extremely powerful to be able to differentiate and learn how to manage. To test for allergy (total Immunoglobulin E) is quite inexpensive and a good place to start. Antihistamine, antibiotics and/or steroids are not the only ways to deal with the symptoms, nor a great long term solution.


True allergy is where your immune system is reacting to either a food or something which is air borne, such as dust, grass, mold, animal dander. The response is an over reaction by the immune system producing antibodies known as immunoglobulin E (IgE). Allergy symptoms usually are related to respiratory and skin areas and can include anyone or more of the following:

  • asthma
  • cough
  • wheezing
  • nasal drip
  • eczema
  • hives
  • persistent runny nose, itchy, congestion
  • hayfever
  • anaphylaxis
  • itching of the throat, eyelids, face, mouth or tongue

Allergy is more common in children, it’s more permanent than food intolerances and usually is related to one or two isolated foods, and/or pollen, fungus spores, animal dander, mould or medicines. The offenders usually need to be avoided long term. It is important to note that digestive infections can elevate IgE. Reactions can occur immediately, but there can be a later reactions about 4 to 6 hours after the initial reaction and persist for days with symptoms like oedema and inflammation. Studies show that antacids impair digestion and can lead to elevation in IgE, considering that this is one of the highest selling drugs on the market it’s probably good to know!

HISTAMINE Intolerance

Interestingly elevated histamine will present as the same symptoms as those in allergy, but the cause is due to histamine excess. related to an inability of the body to clear histamine, causing an overload. Dietary histamine can be rapidly detoxified normally by enzymes known as Diamine oxidase (DAO) and histamine N-methyltransferase (HNMT), but some people have a genetic issues with these enzymes or may be over eating foods which are high in histamine, and the result is impaired histamine degradation, resulting in symptoms mimicking allergic symptoms. This makes it difficult to differentiate between histamine excess and allergy.

  • diarrhea
  • headache
  • rhinoconjunctival symptoms
  • asthma
  • hypotention
  • arrhythmia
  • urticaria
  • pruritus
  • flushing

Foods high in histamine include fermented products such as wine, dry sausage, sauerkraut, miso, soy sauce, scombroid type fish and cheese. In those who have these allergy like symptoms and have a negative diagnosis of allergy (IgE) then histamine intolerance should be considered.

Delayed Intolerances

Other types of intolerances are related to antibodies produced by the immune system which cause delayed onset hypersensitivity reactions to foods, which can take several hours or days for a reaction to occur and can persist for weeks. Immunoglobulin G (IgG) can take up to 3 days and immunoglobulin A (IgA) can take up to 21 days, because of this delay it can be very difficult to determine a food intolerance. Testing for these types of intolerances is more expensive as a panel of many foods needs to be tested, but can be useful if elimination and challenge diets for one reason or another cannot be undertaken or in serious chronic immune diseases. Symptoms can include but not limited to anyone of the following:

  • depression, anxiety
  • gut issues (irritable bowel syndrome, inflammatory bowel disease, constipation, diarrhoea)
  • migraines, headaches
  • fluid retention
  • behavioural problems
  • skin conditions
  • bloating
  • bronchitis, asthma, persistent cough
  • chronic fatigue syndrome, lethargy
  • sleep disturbances
  • stomach aches
  • weight control
  • autism (usually have higher IgG results to casein, protein found in milk, than others)
  • fibromyalgia, body pain and aches
  • runny nose
Interestingly an increased IgG to egg white, orange, wheat or rice can be a predictor to IgE issues to dust, cat, dog hair. IgG antibodies are found in all body fluids and therefore are very common, they fight bacteria and virus and are the only antibodies which can cross the placenta. They common in both adults and children and some of the more commonly reactive foods include cows milk, eggs, beans, nuts, cereals. These reactions are exposure driven, so high consumption of one food may lead to a false positive and no consumption may show a false negative. IgG reactions can be reintroduced after a period of avoidance, this is determined on a case by case situation, but this is very important, as once digestion is improved IgG reactions improve. A result showing many or most foods being reactive requires much attention in improving gut function.


Whilst it is really important in allergy to avoid the the culprit, be that air borne or food, there are some fantastic nutrients, such as quercetin, that stabilise mast cells (part of our immune system) and therefore reduce symptoms. When it comes to histamine intolerance, reducing the intake of dietary histamine foods, alcohol and medicine that produce histamine is useful. Using nutrients such as vitmain B6, vitmain C and copper (should check level before supplementing) have been shown to be effective. With IgG issues foods only need to be avoided for a period of time, depending on the severity of the symptoms, restoring digestive function here is the key and then foods which where a problem usually become less problematic.



Springer link Quercetin
Europe PMC- Antihistamines
BMJ Journals-Drug Reactions

BMJ Journal-Drug use in paediatrics

Science Direct-Antacid medication inhibits digestion

University medical centre-Oral Antihistamines

Annual reviews-Cardiac Actions of Antihistamines

AJ of clinical nutrition-Histamine In tolerances