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Sensitized vs. Allergic: What’s The Difference?

Sensitized allergic

Have you heard of the term sensitized? It’s especially used in connection with allergy tests that identify allergy triggers by detecting your sensitization to specific allergens. But what does being sensitized mean in comparison to being allergic? In this article, we’re going to explain the process of how an allergy develops. We’ll also explain the difference between sensitization and allergies, and the role sensitization plays in allergy testing.

What is an allergy?

To understand sensitization we need to take a closer look at the mechanics of allergy. Allergy is an overreaction of your immune system in response to a substance that is normally harmless.


Substances that cause allergic reactions are called allergens. If you have an allergy your immune system mistakes the allergen as a threat and overreacts to try to protect you.


There are many types of allergies. You can read more about the different types of allergy here. 

What happens when you have an allergic reaction?

In an allergic reaction to substances such as pollen, house dust mites, certain foods, or insect stings, the immune system produces antibodies called Immunoglobulin E (IgE) specific to the trigger it’s trying to fight.

These IgE antibodies tell other cells to release certain chemicals, including histamine. And it’s those chemicals that cause the annoying and sometimes even life-threatening allergy symptoms.

What is sensitization then?

Sensitization is the first step in developing an allergy.


Allergic reactions don’t happen the first time you encounter an allergen. To begin with, your immune system has to meet the allergen. For example, being stung by a bee. Then your immune system memorizes the particular structure of the allergen so that it can produce specific IgE antibodies in defense. This process is called sensitization.


You’re sensitized when you have specific IgE antibodies in your blood. Once you have been sensitized to a particular allergen, your body will produce IgE every time you encounter that allergen again.

When does sensitization usually develop?

Sensitization happens early in childhood and without you being aware of it. The production of IgE begins when a baby is still in the womb. Sensitization to foods like eggs and milk can happen when a baby is a few weeks to a few months old. Sensitization to other allergens in the environment such as pollen, house dust mites, and pets takes a bit more time to develop and usually happens in the preschool or early school years.

Can you be sensitized to more than one allergen?

Sensitization to more than one allergen is common, affecting 10% of the general population and more than half the people with allergy. Being sensitized to just one allergen is sometimes called mono-sensitization. But you can also be sensitized to multiple allergens. This is known as poly-sensitization.

No allergy without symptoms

Sensitization is not the same as an allergy. Sensitization does not always lead to symptoms, but symptoms do not develop without sensitization. In other words, you can be sensitized without being allergic, but you can’t be allergic without being sensitized first.

Sensitized but not allergic

Some people have developed IgE antibodies for a specific allergen but when they come into contact with that trigger again, they don’t experience any allergy symptoms. These people are sensitized but not allergic. In other words, their immune system is sensitive to an allergen or allergens, but they don’t experience any symptoms of allergy.

Sensitized and allergic

For other people, when they are re-exposed to the allergen, they experience allergy symptoms. These people are both sensitized and allergic. Their immune system is sensitive to an allergen or allergens, and this causes symptoms of allergy.

Why are some people just sensitized and others allergic?

We aren’t sure why some people stop at sensitization and others progress to allergy. Our immune systems are highly complex and not all processes and mechanisms are fully understood yet.


We do know that you are more likely to develop an allergy if other members of your family also have an allergy. This doesn’t mean that you inherit a particular allergy, it means you may inherit the tendency towards having an allergy. But there’s always an exception, some people have allergies even if no family member does.

Allergy tests show if your are sensitized to specific allergens

Because it’s possible to detect sensitization, it can be a useful tool for identifying potential allergy triggers. Testing for specific IgE can give you an indication of your sensitization to specific allergens.

So, testing for your allergies to determine if you are sensitized is the very first step to determine if you have allergies, and what those allergies are. 

It’s important to remember that an accurate diagnosis of allergy requires both a test and a consultation with one of our  board-certified allergists. Your medical history is the fundamental link between your allergy test results and being diagnosed with an allergy. Only someone with the experience and know-how can give you a diagnosis of allergy and access to the whole range of allergy management options available to you in your journey to end your suffering.

Don’t let your allergies dictate your life any longer

Take our simple quiz to see if AllergenIQ at-home allergy testing is right for you. 

A journey to a happier, healthier you is only a few clicks away. 

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