A doctor can diagnose food allergies using a variety of tests, including skin prick tests, blood tests, and oral food challenges. Home test kits are also available, though they have several downsides and aren’t widely recommended.

Food allergies affect around 4% of children and 1% of adults worldwide. Food allergies are more common in Western countries, like the United States, and seem to be on the rise.

Keep reading to learn more about what food allergies are, who should get tested, and how food allergy testing works.

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While countless foods can cause allergic reactions in some people, the Food and Drug Administration (FDA) currently lists nine foods as major food allergies, including:

Symptoms of a food allergy may start shortly after ingesting the food, or they may be delayed for a few hours. Common symptoms of a food allergy include:

  • swelling of the tongue, mouth, or face
  • red, itchy bumps on the skin (hives)
  • itching of the lips and mouth
  • wheezing
  • stomach pain
  • nausea, vomiting, or both
  • diarrhea
  • a life threatening reaction known as anaphylaxis

If you or your child have symptoms of a food allergy, consider looking into food allergy testing. There are several ways to test for food allergies, including skin prick tests, blood tests, and oral food challenge tests. Doctors often use a combination of these methods to ensure an accurate diagnosis.

Food allergies vs. food intolerance vs. food sensitivity

While often referred to interchangeably, food allergies, food intolerances, and food sensitivities are not the same, though some of their symptoms may overlap. Here’s what they each mean:

  • Food allergies: Allergies involve an immune response to certain proteins in foods. The immune reaction triggered by food allergies can cause dangerous symptoms that can even be life threatening in certain cases. Food allergies can be immunoglobulin E (IgE)-mediated or non-IgE-mediated. IgE-mediated allergies are considered more severe and can cause life threatening anaphylaxis.
  • Food sensitivities: Food sensitivities are also believed to be immune-mediated, though food sensitivity symptoms aren’t life threatening and are rarely serious.
  • Food intolerances: In contrast to allergies and sensitivities, food intolerances don’t involve the immune system. Instead, food intolerances occur due to difficulties digesting certain foods.

Symptoms related to food sensitivities and intolerances aren’t dangerous, but they cause discomfort and significantly affect your quality of life. Such symptoms can include diarrhea, bloating, stomach pain, and rashes.

Another difference between intolerances, sensitivities, and food allergies is that it may take only a trace amount of a certain food to trigger severe allergic reactions. Intolerances and sensitivity symptoms, on the other hand, are commonly dose dependent. This means a person will have a more severe reaction if a larger amount of the food is consumed.

While food allergies are most commonly diagnosed with allergy testing, intolerances and sensitivities are more difficult to diagnose and may only be identified through using elimination diets.

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Most food allergies develop early in life, during childhood. Yet they can develop at any age, which means a food allergy could develop during adulthood. A food allergy will trigger some sort of symptom every time you eat the food or foods to which you’re allergic.

Keep in mind that food allergy symptoms can vary in severity, and you may not have the same reaction every time you eat a food you’re allergic to.

If you suspect you or your child may have a food allergy, it’s critical to visit a healthcare professional, like an allergist, to undergo appropriate testing.

Several types of tests are commonly used to diagnose food allergies, including skin prick tests, blood tests, and oral food challenges. Here’s a closer look at each.

Skin prick tests

After taking a detailed personal and family history, healthcare professionals typically use a skin prick test first when trying to diagnose a food allergy.

In general, skin prick tests provide a rapid means to detect food allergies and are cost-effective.

What to expect

Skin prick tests involve placing a small amount of liquid extracts of certain foods on your skin, usually on your back or arm. Next, the healthcare professional uses a small tool to lightly prick your skin, allowing some of the food extract to get below your skin’s surface.

They may also test for nonfood allergens, such as pollen. This is because people allergic to pollen can also experience an itchy mouth and throat after eating certain fruits and vegetables, such as apples or kiwis.

The reaction occurs because the proteins found in these foods are similar to those found in pollen, which can confuse the immune system. Allergists refer to this as oral allergy syndrome or pollen fruit syndrome.

After 15–20 minutes, they’ll examine the area for any signs of an allergic reaction, such as bumps or a rash.

Considerations

Though a positive test result indicates the possibility of reactivity to a food, it doesn’t necessarily mean you have a food allergy. In fact, up to 60% of positive skin prick tests do not reflect symptomatic food allergy. So your doctor may have to use other tests, like an immunoglobulin E (IgE) blood test, to rule out or diagnose a food allergy.

Skin prick tests also aren’t appropriate for everyone, including people who:

  • have certain skin conditions
  • are taking certain medications
  • are at an increased risk of having a serious reaction to skin prick testing

Blood tests

An allergy blood test measures the amount of IgE in your blood. There are two types of allergy blood tests:

  • Total IgE test: measures the total amount of IgE antibodies in your blood
  • Specific IgE test: measures the amount of IgE your body produces in response to a single type of allergen

Your healthcare professional might perform an allergy blood test after a skin prick test or when they cannot perform a skin prick test.

Blood tests may also be preferred over skin prick tests in young children, as skin prick tests may be too uncomfortable for them.

What to expect

To do a blood test, a healthcare professional will take a small sample of your blood and send it to a laboratory. In the lab, the sample will be exposed to different foods.

If your blood releases a lot of IgE antibodies in response to a particular food and you have symptoms when you eat that food, you’re likely allergic to it.

Considerations

Unlike skin prick tests, which yield quick results, blood test results can take several days to get back. The test is also usually more expensive than a skin prick test, though some health insurance plans will cover the cost.

As with skin prick tests, blood tests can produce false positives. You may need to follow up with an additional test in the weeks or months after the initial one.

Oral food challenges

If skin pricks and blood tests don’t produce clear results, your healthcare professional may have you do an oral food challenge. This is generally done in a doctor’s office under close supervision, as it can sometimes cause a severe allergic reaction.

An oral food challenge is considered to be the most reliable and definitive food allergy test because it provides quick results that are easy to identify.

This test is also helpful for adults looking to find out whether they still have a food allergy from their childhood. For example, allergies to milk, eggs, wheat, and soy often resolve with age.

What to expect

To prepare for an oral food challenge, suspect foods are typically eliminated from the diet for 7 to 14 days before the challenge. This increases the likelihood of a definitive result. You must discontinue medications that could interfere with the results, such as antihistamines and b-adrenergic bronchodilators, before oral food challenge tests.

During an oral food challenge, you’ll be given a small amount of food while your doctor checks for signs of a reaction. If you don’t have a reaction, they’ll gradually increase the amount of food. If you don’t have a reaction to this larger amount, you can likely rule out a food allergy.

If the test result is negative, your healthcare professional will rule out a false negative with supervised feeding using a typical serving of the food in question. A false-negative oral food challenge result can occur in 1–3% of cases.

If an oral food challenge does detect a food allergy, you will have to completely remove the allergen from your diet to avoid allergic reactions.

Considerations

Unlike skin prick or blood tests, oral food challenges require avoidance of suspect foods for 7–14 days leading up to the test. Additionally, you could experience a severe allergic reaction during testing.

What about elimination diets?

Elimination diets are sometimes used to help pinpoint specific foods that might be causing symptoms of an allergic reaction. They can also help confirm the results of skin prick or blood tests.

On their own, though, they can’t be used to distinguish between a true food allergy and an intolerance or sensitivity, which are less severe.

During an elimination diet, you’ll avoid eating certain foods for several weeks. Then, you’ll slowly add them back in one at a time. Each time you reintroduce a food, you’ll check for symptoms of an allergic reaction, such as:

  • a rash
  • diarrhea
  • vomiting
  • a runny nose

It’s best to keep detailed notes in a journal about what you eat each day and any symptoms you have. If you don’t have any reaction to the reintroduced food, you can assume you aren’t allergic or sensitive to it and move on to reintroducing the next food.

If you want to do an elimination diet, it’s important to do it with the help of a healthcare professional, such as a doctor or registered dietitian, to avoid nutrient deficiencies, which can cause their own set of symptoms.

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Yes, there are a variety of at-home food allergy kits you can order online or purchase in drugstores.

Most kits have you prick your finger and send a blood sample off to a laboratory. Other kits require sending in a sample of your hair. After analyzing your sample, the company will give you your test results.

At-home food allergy tests aren’t generally recommended

Despite their widespread availability, many healthcare professionals do not recommend at-home allergy tests because of concerns about safety and reliability.

For example, most tests are based on outdated and questionable research and use controversial methodologies.

Food allergy testing generally relies on seeing whether your blood produces IgE antibodies in response to certain foods. But most home tests only measure immunoglobulin G (IgG) antibodies.

There’s no evidence that this can help diagnose a food allergy. In fact, according to the American Academy of Allergy, Asthma, and Immunology (AAAAI), the presence of IgG in the blood is a typical immune response to food exposure, and having higher levels of IgG antibodies to specific foods may actually indicate tolerance, not an allergy.

A 2022 study found that just 1 of 22 food allergy test kit companies used an accredited laboratory, performed IgE testing, and had a clinician involved in the testing process. All of the other companies used unaccredited laboratories and controversial, unreliable testing methods.

It’s also worth noting that while at-home tests may seem less expensive than a doctor’s visit, most insurance plans don’t cover at-home test kits. Because of this, your out-of-pocket cost may be higher with at-home tests, depending on your coverage.

A note on at-home food allergy tests

The AAAAI currently does not endorse the use of at-home allergy testing. Additionally, at-home food allergy tests cannot officially diagnose a food allergy. Instead, they can help identify foods that you have the potential to be allergic to.

If you’re interested in at-home testing, the following three IgG-based tests passed Healthline’s vetting process, have clinician involvement, and use accredited laboratories:

Still, keep in mind that if your results suggest that you may have a potential allergy, make an appointment with an allergist to ensure accurate interpretation and establish a follow-up plan.

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There’s no cure for food allergies, and the only treatment is strict avoidance of the offending allergen or allergens.

You must be aware of products that contain the food or foods to which you’re allergic and be diligent about reading ingredient labels and making food workers, such as waiters, aware of your food allergy.

If you’re allergic to multiple foods or are unsure of what products contain ingredients that might trigger an allergic reaction, it’s recommended to work with a healthcare professional who specializes in food allergies, such as a registered dietitian or allergist.

They can help you identify products that contain allergens and develop an allergen-free, nutritionally complete eating pattern.

Your healthcare professional may prescribe medications, such as epinephrine and antihistamines, which people at risk for developing anaphylaxis should carry at all times. These medications are used in case of accidental exposure to an allergen and can save your life if you experience allergic symptoms such as throat swelling, shortness of breath, and low blood pressure.

In addition to providing medical advice and prescribing necessary medications, your healthcare professional can answer any questions you may have about how to keep yourself safe and healthy while living with a food allergy.

An oral food challenge test is considered the gold standard of food allergy diagnosis. It’s sometimes used to confirm a suspected food allergy. However, since this test may trigger life threatening reactions, it should be administered by trained healthcare professional in a medical setting only.

Allergy tests administered by trained healthcare professionals are the safest and most accurate way to diagnose a food allergy. Allergy experts do not recommend at-home food allergy testing kits, as most use controversial and ineffective testing methods.

Food allergies can cause potentially serious reactions, so it’s important to get properly tested if you think you might have a food allergy. While home test kits offer tempting convenience, they aren’t very reliable.

Work with a doctor or other healthcare professional to help confirm whether you have a food allergy. They can also help rule out other causes of your symptoms, such as a food intolerance or sensitivity, which are different from an allergy.