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How to Find Food Sensitivities and Allergies to Cut Eczema Breakouts

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Certain food allergies can trigger or worsen eczema breakouts. The most common food allergies linked to eczema are milk allergy and wheat allergy. However, before treatment is recommended, you need to find the specific food allergy responsible for your eczema. This is also important because simply avoiding foods you are allergic to may help you stay eczema-free. This article discusses the various diagnostic investigations used to determine food allergies and sensitivities and also identifies their limitations.

Food Allergies and Eczema

Food allergies are hypersensitivity reactions to certain food proteins. Unlike food intolerance, food allergies are due to immune reactions to food proteins recognized as allergens.

In response to this allergens, the body raises immunoglobulins to act as antibodies. Immunoglobulin E or IgE is especially linked to atopic eczema. Besides antibody response to food allergens, the release of histamine in the tissues of the skin can also contribute to the symptoms of eczema.

Eczema caused by food allergies can be resistant to conventional treatment. However, such cases are easily treated by eliminating the offending food from your diet.

Therefore, finding the food allergy responsible for your eczema is important to getting quick relief.

Common Food Allergies
  • Cow’s milk allergy
  • Wheat allergy
  • Peanut allergy
  • Tree nut allergy
  • Egg allergy
  • Fish allergy
  • Soybean allergy

The first step to determining whether your eczema is due to food allergies is to visit your doctor or an allergist and request to be tested for food allergies.

Discussed below are the different diagnostic investigations used to confirm food allergies as well as some of the less popular controversial tests.

Patient History

The first step is to tell your doctors about your eczema symptoms and the food allergies you suspect.

Your doctor will need to know how soon your eczema flares up after eating the foods suspected, how much you ate and any other pattern you may have noticed.

Your doctor will also ask about any allergy disease you may have or had before as well as family history of food allergies.

The conversation with your doctor or allergist should also cover your exposure to common eczema triggers.

Therefore, your choice of beauty products, soaps and detergents are some of the questions that will be asked because these products can also irritate sensitive skin types and repeatedly trigger eczema flare-ups.

Physical Examination and Investigations

Your doctor may also give you an extensive physical examination to identify any other medical problems you have in order to rule out those conditions as the cause of your eczema symptoms.

Descriptions of your home and work environment may also be required in order to rule out environmental toxins such as heavy metals as the cause of your eczema.

In addition, certain infections (candida infections, for example) may be responsible for your eczema.

Therefore, your doctor may order blood tests to rule out systemic and skin infections as causes of your eczema.

Food Diary

Keeping a food diary is a more reliable way of determining the relationship between food allergies and eczema than simply recalling them.

A food diary or log will provide details about the foods you ate as well as when and how much of it you ate. By comparing the appearance and severity of your eczema with the content of your food diary, your doctor should be able to identify patterns that suggest a link between food allergies and your eczema.

The content of your food diary can also help your doctor decide the right food allergy tests to recommend as well as the appropriate time of the day to take the test.

Lastly, a food diary makes the results of your food allergy tests more informative. By comparing your own reports of the allergy and eczema symptoms with test results, your doctor can interpret the results more accurately.

Skin Prick Test

A skin prick test is the most common method of diagnosing allergies. It is meant to trigger a small and controlled allergic reaction to the test allergen. Ideally, a skin prick test is done on the forearm.

In preparation for a skin prick test, your doctor should ask you to avoid medications that may affect its result. Such medications include antacids, antidepressants and antihistamine drugs.

Antihistamine drugs are especially to be avoided because they block the release of histamine in skin tissues. Because itching and the appearance of hives are dependent on the ability of the food allergen to trigger the release of histamine, antihistamine drugs make skin allergy tests ineffective.

For the actual test, a grid of dots is drawn on the skin and then small amounts of known and suspected allergens are delivered under the skin by pricking it with needles or pins.

The appearance of a rash or hives indicates that you are sensitive to the allergen injected at that spot on your skin.

To confirm that the test is working, a known allergen such as histamine and a non-allergenic substance such as glycerin are also added to the test panel along with the food allergens suspected.

Ideally, histamine should trigger an allergic reaction and glycerin should not. If these outcomes are not achieved then the test result is considered false.

The Limitations of Skin Prick Test Results

A skin prick test is not a confirmatory test for food allergies. It is rather used as an exploratory test.

This means that only a positive result is useful and even then it is not enough to confirm that you have a food allergy. Besides, the hypersensitivity reaction that denotes a positive result for skin prick test is mediated by the immunoglobulin, IgE.

Therefore, skin prick test cannot detect allergies caused by immunoglobulin antibodies other than IgE.

Even when the food allergen suspected fails to trigger a skin reaction, the negative result may mean that concentration of the allergen used is too low or that the food allergy is driven by a slow-onset hypersensitivity reaction rather than an immediate anaphylactic reaction.

Skin Patch Test

A variation of the skin prick test is the patch test. In this case, a patch containing test allergens is applied on the skin rather than introducing the allergens with pinpricks.

The test patch is usually placed on the skin of the back. Once applied, the subject is advised not to take a bath or exercise for the next 48 hours.

Blood Test

Your doctor may also order blood tests to investigate your food allergies. Blood tests for food allergies measure the antibody response to food antigens.

Like skin prick test, blood test for allergies can only detect allergens that trigger IgE antibodies. Therefore, it is useless against allergens that trigger the release of other antibodies besides IgE.

However blood test has one advantage over skin prick test: it can test for many allergens at the same time.

The most common form of blood test for food allergies is known as RAST (RadioAllergoSorbent Test).

RAST measures the amount of IgE produced against a specific antigen. A more specific RAST test is CAP-RAST. It can measure the level of IgE produced in response to each of the allergen tested.

The result of a RAST test is presented as a score. This score is then compared to a predefined set of predictive values. There are currently predictive values for allergens of milk, wheat, soy, fish, egg and peanut.

When your score is above the predictive value for a food allergen then there is a very high probability (above 95%) that you are allergic to that food.

Because blood tests can screen hundreds of allergens at once, it is possible to use it to screen for more than food allergies. Therefore, it produces a more comprehensive picture of your allergies than skin prick test.

Elimination Diet

An elimination diet or exclusion diet is used to determine whether the removal of a food, suspected to be responsible for allergic reaction, from the diet will improve the symptoms of a food allergy.

If a food allergy is indeed involved in the appearance of your eczema then the eczema should resolve within 2 – 4 weeks after eliminating the food from your diet and re-appear after a little interval when the food is re-introduced to your diet.

Therefore, an elimination diet is a more rigorous food allergy and sensitivity test than skin prick test and a more specific test than RAST test.

The 3 stages involved (challenge with the food, elimination of the food allergy and reintroduction of the food allergen) can help catch food allergies that do not cause immediate allergic reactions. This means that an elimination diet can help diagnose slow-onset hypersensitivity reactions to food allergens.

The other foods allowed in an elimination diet must be only those unlikely to trigger the allergic condition.

If one of the foods in the elimination diet is still causing your eczema, then that food needs to be excluded and a new elimination diet must be designed.

A strict adherence to an elimination diet is important because even the smallest exposure to one of the offending foods can make the results of this test invalid. Therefore, people placed on elimination diets are encouraged to keep a log of all foods eaten, drugs taken and symptoms experienced.

The minimum duration of an elimination diet is 2 weeks. If there are no changes in eczema symptoms after 4 weeks, then it is unlikely that the excluded food is responsible for your symptoms.

If the eczema resolves while placed on an elimination diet, a re-challenge with the excluded food must be done in order to confirm that the re-appearance of symptoms is truly due to the presence of the food.

However, at least 5 days is allowed after the elimination diet (when all prior symptoms of eczema has cleared) before the re-challenge test.

Elimination diet is rarely used to fully diagnose food allergies responsible for atopic eczema. This is because it is not a foolproof test and its results can be influenced by psychological factors. To reach an unbiased diagnosis of a food allergy, an oral challenge test is conducted.

Oral Food Challenge

Unlike an elimination diet, an oral food challenge is conducted in the doctor’s office and under his supervision.

There are 3 types of oral food challenge: open, single-blind and double-blind placebo-controlled oral food challenge tests.

Open oral food challenge is the simplest. It requires that you take small but increasing amounts of the suspected food to see if you develop allergic reaction to it.

Single-blind oral food challenge differs from the open challenge because you do not know the specific food given to you (but your physician knows). This eliminates previous bias you may have had towards foods you have suspected to trigger your eczema.

However, the most reliable test is the double-blind, placebo-controlled oral food challenge (DBPCFC).

In the double-blind challenge, the specific food given to you is masked with another food (a vehicle) and a non-allergenic food (placebo) with similar appearances is also given.

The health professional administering this test would not know which one of the two foods given is the challenge food and which is the placebo. In addition, both the test food and placebo food are randomly given.

Oral food challenge is effective for diagnosing food allergies involving IgE and other immunoglobulins.

Based on its results, your doctor may recommend the right treatment and diet for your eczema.

Unproven Food Allergy Tests


VEGA testing or electrodermal testing employs the principles of electroacupuncture for detecting the root cause of recurring health problems.

Naturopaths who use VEGA testing believe that it detects disharmony in the energy flow of the body rather than structural abnormalities.

Basically, a VEGA test measures changes in the electrical resistance property of the skin. Proponents of VEGA testing believe that allergies can produce such changes. Therefore, a galvanometer is used to measure skin conductance.

First, a patient is placed inside the machine and then the food allergen (kept in a sealed glass vial) is placed on an aluminum plate within the circuit of the machine.

Then the galvanometer measures changes in resistance to electrical conduction in the skin of the patient.

A drop in electrical conductance is taken as proof of allergy or intolerance to the food placed in the glass vial.

There is no scientific support for the use, principles and results of VEGA testing. Multiple studies and reviews found it ineffective for diagnosing any kind of allergy and its use is therefore not recommended.


ALCAT or antigen leukocyte antibody test is used to test for food allergies and has been claimed to help detect non-IgE allergies.

The ALCAT test is a variation of another unproven test known as the leucocytotoxic test.

It involves introducing a test food allergen to whole blood sample from the patient and then measuring changes in the diameters of the white blood cells found in the blood.

Although it was developed by an American medical diagnostic company and used in some countries, there is no scientific support for the determination of allergies by measuring white blood cell diameters nor is there clinical proof to support the efficacy of this test.

Like the VEGA testing described above, the result of this test cannot be accurately reproduced and it is not recommended for determining whether your eczema is caused by food allergies or not.

Applied Kinesiology

Applied kinesiology is the study of the muscles and the relationship between muscle strength and general health.

Proponents of applied kinesiology believe that the definitive sign of ill-health is muscle weakness.

In food allergy testing with applied kinesiology, the patient is asked to hold a glass vial containing the suspected food allergen in one hand while the kinesiology practitioner applies light pressure on the muscles of the other arm.

The patient is believed to be allergic to the food allergen he is holding if the muscle weakness is detected in the other arm.

Not only did studies find applied kinesiology useless for allergy testing, there is simply no relationship between muscle weakness and immunoglobulin-driven allergic reactions.

Therefore, the procedure is not recommended for allergy testing by any national or professional health regulatory body.

Next Article: Eczema and Zinc