Sensitization and True Allergy

The process by which your body becomes sensitive to—and allergic to—a particular substance is called sensitization. When your immune system becomes sensitized to an allergen (an otherwise harmless substance), you will likely develop symptoms of an allergy each time you are exposed to that same allergen.

Allergies can include physical reactions that range from mildly uncomfortable to severely harmful.

A young girl with allergies in the daylight
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Allergens trigger an immune response in some people and not in others. The process of sensitization is complex, involving steps in which your body "learns" to produce an inflammatory reaction and remembers to do so whenever you are re-exposed to the allergen.

Symptoms of Sensitization and True Allergies

Sensitization is a process by which the immune system will produce an antibody, which is a defensive protein, in response to a substance—such as certain foods, pollen, mold, or medications.

As such, allergy symptoms develop due to the reaction triggered by the immune system in response to the allergen. If there are antibodies but no symptomatic response, we refer to that as asymptomatic sensitivity.

Allergy symptoms may include:

  • Skin rash
  • Hives
  • Itching of the eyes or skin
  • Wheezing
  • Rhinitis (nasal drip, sneezing, congestion)

In more severe hypersensitivity reactions, anaphylaxis, a severe form of allergy, can develop. This allergic response can lead to respiratory distress, shock, and even death.

Variations in Allergic Sensitivity

Interestingly enough, allergy sensitization not only varies by the individual, but also by which part of the world you live in. For example, sesame allergy is common in Israel, where peanut allergy is rarer. Conversely, peanut allergy is common in the United States, where sesame allergy is rarer. If you live in Italy, you are more likely to be allergic to fish.

While scientists aren’t entirely sure why this happens, some believe that the widespread consumption of certain foods within a region will allow individual exposure and subsequent sensitization that manifests with a higher incidence of a particular allergy.

And the way certain foods are processed (or even the soil where they grow) may contribute to the phenomenon. The same applies to pollutants or toxins that are prevalent in certain parts of the world and less so in others.

Cross-Reactive Sensitivity

If a person has a true allergy, the presence of the allergic antibody will typically be present in the bloodstream. As such, wherever a person is re-exposed to an allergen, the antibody will be there to trigger a response, and sometimes the antibody can be detected with a blood test.

In some cases, the immune system will mistake a non-allergen for a true allergen. This is called cross-reactivity and occurs when the protein of an allergen—like pollen—is similar in the structure of something else.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.