Atopy Patch Testing for Foods: The Information You Need to Know

Your day is planned around your stomach pain and trips to the bathroom. Gas, bloating, discomfort are your norm. You feel that food is a trigger, but you just can’t figure out which food it may be. You are not alone. We know that foods can affect symptoms in eczema, EoE and IBS. However, given reactions are delayed, it can be difficult to pinpoint the trigger on your own.

Types of Food Reactions

Atopy Patch Testing for foods and food preservatives was first performed in 1990s in Europe and in the early 2000 in the United States (American Partnership for Eosinophilic Disorders, 2025). In order to understand patch testing for foods, we must first understand the different types of available food testing and what each is intended to identify. There are two basic types of food reactions- those that are IgE mediated and those that are cell mediated. IgE reactions occur within minutes of eating the trigger food and can result in severe symptoms such as throat closing, trouble breathing and in severe cases death. An example of this is a child with an anaphylactic peanut allergy. Within minutes of eating the peanut, the child may have severe, life threatening symptoms. In contrast, cell mediated reactions are delayed and not life threatening. This types of reactions may occur hours or even days after eating the trigger food. An example of this may be an adult who develops gas, bloating, and stomach pain after eating soy.

Scratch or Skin Prick Testing

The most common type of testing for foods is the scratch test. A scratch test uses standardized food extracts that are commercially prepared and purchased by the office that performs the testing, These extracts are placed on the skin and a plastic applicator is used to scratch or puncture the very top layer of the skin. After 15 minutes, the site is evaluated for redness and welting. This form of testing is looking for an IgE mediated allergy- the type of reaction that is immediate and potentially severe.

Patch Testing

Patch testing evaluates for delayed, cell mediated reactions. This test involves applying pureed foods and food preservatives on the skin in small amounts and leaving these products on the skin for 48 hours. After this time, the patches are removed and the site is evaluated for redness and rash. If inflammation occurs at the site, the thought is that this food may also be causing similar inflammation when ingested as part of your diet. In patch testing, the food purees that are used on the test are not commercially available. Therefore, studies have shown some variability between testing results from one office to another. However, the food preservatives are standardized and are purchased from a commercial manufacturer. 

We know that for many disorders, such as IBS, EoE and atopic dermatitis, the relationship between the inflammation and foods ingested is delayed. Although many offices still perform IgE testing to help identify triggers for these disorders, we know that these disorders are not triggered by IgE mediated mechanisms (although the co-existence of IgE mediated food allergy is more common in those with eczema). Although it is common for scratch testing panels to be used to identify sensitivities or delayed reactions, current guidelines advise against this given the poor specificity and the fact that these panels are not intended to identify cell mediated reactions. In 2014, the American of Allergy, Asthma and Immunology released a statement discouraging the use of IgE testing without a history consistent with potential IgE mediated food allergy. When these scratch tests are performed as screenings, there can be multiple false positives, which often results in the avoidance of foods that do not need to be avoided (Parrish, 2023). Atopy patch testing is a tool that helps identify the delayed reactions so we can have a guide as to which dietary modifications may improve symptoms.

Which Test Do I Need?

Both atopy patch testing and scratch testing play an important role in the diagnosis of food allergies and sensitivities. Which test is right for you depends upon you history and symptoms. In some cases, individuals may benefit from both tests. Discussing symptoms with your provider will help your provider choose the appropriate test to guide your treatment plan.

If you want to know if atopy patch testing could help you, schedule your appointment with Monarch Medical so our experienced nurse practitioners can help you navigate your options.

References

American Partnership for Eosinophilic Disorders. (2025). https://apfed.org

Parrish, Christopher. (2023). A Review of food allergy panels and their consequences. Annals of Allergy, Asthma & Immunology, 131(4), 421-426.