What is the difference between Allergy & Sensitivity?

The incident of allergy and sensitivity is growing at an alarming rate. As an allergy practitioner, I see on a daily basis growing numbers of people experiencing allergy and sensitivity symptoms.

Common Allergy and Sensitivity Symptoms.

  • Digestive issues such as bloating, cramping, pain, flatulence, diarrhoea and constipation.
  • Skin rashes, itchy skin, dry skin, recurring skin infections.
  • Headaches, migraines, generalised aches and pains.
  • Sneezing, itchy eyes, sinus congestion.
  • Generalised fatigue and recurring infections.

I see these symptoms on a daily basis in the allergy clinic. Despite the growing number of allergy and sensitivity patients, it is still an area of medicine that for the most part is poorly understood.

I routinely sit down with patients who present with signs that they are reacting to foods who will say, “I have been tested and I have no allergies” and have not modified their diets because of this. The first place I start with these patients is to explain the difference between allergy and sensitivity and how this impacts testing options and treatment recommendations.

What is Allergy and Sensitivity?

Generally, both allergy and sensitivity can be seen as errors in the body’s immune system. The immune system plays a vital role in protecting the body against foreign substances such as a virus, bacteria, toxins etc. In both allergy and sensitivity, the immune system makes a mistake. It perceives something that is usually harmless as a threat and reacts to it.

Eg the body thinks pollen is bad and works to expel it, causing sneezing, mucus etc.

The immune system generates inflammation to neutralise and remove this perceived threat. Swelling, itching, mucus, sneezing, redness, etc are all symptoms that result from the immune system generating inflammation against the threat. The problem is it is reacting to things it should not be eg dust, pollen, food components and generating inflammatory symptoms unnecessarily.

The difference between allergy and sensitivity lies in how the body goes about generating the inflammatory response to the perceived ‘threat’.


An allergic reaction involves the generation of a component of the immune system called IgE antibodies. These antibodies are produced in response to a perceived threat and work to generate inflammation to neutralise the threat. These reactions are typically fast acting, they occur immediately after exposure and can be triggered by very small amounts of exposure to a given allergen. Ig E responses are involved in severe allergic reactions such as anaphylactic reactions. Common food components that cause IgE allergic reaction include Peanuts, Egg, Fish, Shellfish, Dairy and Soy. Common airbourne components that cause IgE allergic reactions include pollens, grasses, mould and dust mites.


Sensitivity reactions also involve an error in the immune system however unlike allergy these reactions do not involve an IgE antibody response. We are still learning about the mechanisms of sensitivity reactions. What we do know is that they are a result of the body reacting to components that are usually harmless. Sensitivities result in the generation of inflammation and symptoms.

Sensitivity symptoms are similar to allergy symptoms, they can be seen in the gut such as bloating, in the respiratory system such as running nose and sneezing, in the skin such as skin rash and itching and in the nervous system such as fatigue and pain. Unlike allergy symptoms, sensitivity symptoms are often not immediate. They can involve delayed reactions. Sensitivities also work on thresholds of exposure to trigger symptoms.

In allergy, a small amount of exposure can cause a reaction. With sensitivity, most people have a level of tolerance and need exposure to exceed this level before symptoms are triggered. In Allergy people are usually aware of the substance causing the problem. In sensitivity due to the delayed reaction and threshold of tolerance people often do not know the substances are causing their symptoms.

Testing Options for Allergy & Sensitivity

It is important to understand the difference between allergy and sensitivity to understand which testing options will be the most beneficial for your symptoms. Patients will commonly present with sensitivity symptoms and wish to do “allergy testing”.

Allergy Testing

Allergy testing is usually done through your doctor or specialist and involves the assessment of IgE mediated reactions. This may involve IgE Specific blood testing or skin prick testing. It is important to understand that these tests only assess IgE mediated reactions and cannot confirm or exclude sensitivity reactions.

When a patient comes to me and says I have done allergy testing and I do not react to any foods I need to explain that there may not be an allergic reaction however there may be a sensitivity reaction causing symptoms.

It is also important to understand that IgE testing cannot be used alone to diagnose an allergy. In some cases, you may test negative to something you know you have a reaction to or you may test positive to a substance you do not react to. Medical guidelines recommend using these tests to confirm a reaction to a substance you have already observed symptoms with. You will not be diagnosed with an allergy in the absence of clinical symptoms regardless of the test results.

Due to the margin of error in allergy testing, we always have to take into account clinical symptoms and reactions you have observed when making an allergy assessment.

Sensitivity Testing

As sensitivity reactions do not involve an IgE mediated immune response they will not show in standard IgE allergy tests. There are a number of Functional tests available to us to assess sensitivities however again a margin of error applies and results should always be interpreted in relation to clinical symptoms.

IgG testing: This involves testing for the IgG antibody to various foods. In practice, I do not use this test in my clinic as I find it does not correlate well to clinical symptoms. The IgG antibodies can be produced as part of the normal process of developing tolerance to food and can often just reflect that that food is being consumed in the diet.

ALCAT Testing: ALCAT testing measures the blood cells inflammatory response to a variety of foods. I like ALCAt testing as a sensitivity guide. However, ALCAT does not identify IgE allergies and can miss components causing reactions, and include substances not causing clinical symptoms. For this reason, I use it alongside an elimination/rechallenge diet for best results in the identification and management of allergies and sensitivities.

Elimination/Rechallenge Diet: I find the elimination/rechallenge diet to be easily the most effective strategy for identifying sensitivities. In our clinic, each patient is put on an elimination/rechallenge diet according to their individual symptoms. We also offer sensitivity retraining to strengthen the body to substances that cannot be avoided. This process also includes work to reduce the drivers of inflammation such as working to restore gut health and calm nervous system stress. Through this process, we are able to reduce inflammation to the point where people are able to clearly see problem foods on reintroduction. The downside of this process is that it requires work, you must commit to a 4-6 period on an elimination diet. The upside of this process is that it gives you a life long strategy to be able to identify the components contributing to your symptoms.

Rachael Reed – The Allergy Naturopath

Learn More

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Rachael Reed

Rachael Reed

The Allergy Naturopath

Rachael Reed is a university qualified Naturopath with a background in science and research. She has a wealth of knowledge with 14 years of clinical experience specialising in allergy and sensitivities. Rachael is an author, trainer and educator. As a sufferer of allergy and sensitivity symptoms, Rachael has an in-depth insight into understanding and managing these symptoms.