Food Allergy Testing: How Does It Work?

If you or your child has had a concerning reaction to food, determining whether you have a true food allergy starts with a careful evaluation. Katherine McCormack, MD, a board-certified allergist at Boulder Medical Center in Louisville, Colorado, explains how allergists evaluate food allergies and when to recommend skin testing, blood testing, or an oral food challenge.

How Are Food Allergies Diagnosed?

Food allergy evaluation begins with a detailed medical history. Your allergist will ask about the foods involved, how often you have eaten them, the symptoms you experienced, how quickly those symptoms developed, and whether you have other allergic conditions.

Based on your history, your allergist may recommend additional testing to help determine whether a food allergy is present.

Skin Prick Testing for Food Allergies

A skin prick test, sometimes called a scratch test, is a common initial test used to check for immediate allergic reactions to specific foods.

During the test, a small amount of food extract is placed into a very light scratch or prick on the skin. The area is then monitored, typically for about 20 minutes.

If a hive develops at the test site, it may indicate an allergy to that food. If the skin does not react, the food is less likely to be a true allergen.

Blood Testing for Food Allergies

Sometimes a skin prick test isn’t possible. This may be the case if a patient cannot stop taking antihistamine medication or has severe eczema that interferes with skin testing.

In these situations, a blood test may measure antibodies associated with an allergic response.

What Do Food Allergy Test Results Mean?

Skin and blood tests are only part of a food allergy evaluation. False-positive results can occur, particularly when there is no history of a reaction consistent with a food allergy.

That is why an allergist considers test results alongside your symptoms and medical history, rather than relying on a positive skin or blood test alone.

If your medical history and testing don’t provide a clear answer, your allergist may recommend an oral food challenge (OFC).

What Is an Oral Food Challenge?

An oral food challenge is a medical procedure used to help determine whether someone is allergic to a particular food.

During an oral food challenge, the patient eats pre-measured amounts of the food in gradually increasing doses while staff closely monitor for an allergic reaction.

Because of the possibility of anaphylaxis, a severe and potentially life-threatening allergic reaction, an oral food challenge must be supervised by an allergist and/or medical team trained to recognize and treat anaphylaxis.

Never perform a food challenge at home unless your allergist specifically directs you to do so.

Let’s Talk

If you or your child has experienced a concerning reaction to food, an allergist can help determine whether food allergy testing or further evaluation may be appropriate. BMC board-certified allergy specialists provide food allergy evaluation, testing, and treatment for children and adults in Boulder and Louisville, Colorado.

Meet Our Allergy, Asthma & Immunology team and make an appointment.