What doctor tests for food allergies
Imaging is not typically used in diagnosing food allergies.
Endoscopy and biopsy might be recommended if you are experiencing digestive tract bleeding, chronic constipation or diarrhea, or severe persistent stomach pain. That said, this study is more typically used to check for celiac disease, which is an autoimmune reaction to gluten.
Using an endoscope, a flexible tube with a light and camera, your doctor can view images of your little intestine on a digital monitor and take a sample of tissue (biopsy) for evaluation in the lab. For this test, the endoscope is lowered into the stomach, generally through your esophagus.
Referral to an allergy clinic
If your GP suspects a food allergy, you may be referred to an allergy clinic for testing.
The tests needed can vary, depending on the type of allergy:
- if the symptoms developed quickly (an IgE-mediated food allergy) – you’ll probably be given a skin-prick test or a blood test
- if the symptoms developed more slowly (non-IgE-mediated food allergy) – you’ll probably be put on a food elimination diet
During a skin-prick test, drops of standardised extracts of foods are placed on the arm.
The skin is then pierced with a small lancet, which allows the allergen to come into contact with the cells of your immune system.
Occasionally, your doctor may perform the test using a sample of the food thought to cause a reaction.
Itching, redness and swelling generally indicates a positive reaction. This test is generally painless.
A skin-prick test does own a little theoretical chance of causing anaphylaxis, but testing will be carried out where there are facilities to deal with this – usually an allergy clinic, hospital, or larger GP surgery.
An alternative to a skin-prick test is a blood test, which measures the quantity of allergic antibodies in the blood.
Food elimination diet
In a food elimination diet, the food thought to own caused the allergic reaction is withdrawn from your diet for 2 to 6 weeks.
The food is then reintroduced.
If the symptoms go away when the food is withdrawn but return once the food is introduced again, this normally suggests a food allergy or intolerance.
Before starting the diet, you should be given advice from a dietitian on issues such as:
- the food and drinks you need to avoid
- if any alternative sources of nutrition are needed
- how you should interpret food labels
- how endless the diet should final
Don’t attempt a food elimination diet by yourself without discussing it with a qualified health professional.
Your doctor will likely enquire you to take several steps at home that will assist determine if you own a food allergy.
These steps include keeping a food and symptom diary and, perhaps, participating in an elimination diet—both of which can provide helpful diagnostic information.
Keeping a Food Diary
If your doctor is unsure whether food is the cause of your symptoms, he or she may recommend that you hold a food diary. A food diary can also be used to monitor dietary patterns to better pinpoint the cause of your symptoms.
The diary should be a finish record of not only the foods you've eaten over a given period of time (usually a week), but also an accurate record of the timing and characteristics of any symptoms you may own experienced.
Your doctor may go so far as to enquire you to record any activities you may own done prior to your symptoms to assess whether they may own contributed.
In some cases, stress and physical exertion can frolic as much a role in your symptoms as the foods you eat.
A food diary is often used in combination with other diagnostic tools or as a first step in opening an investigation.
Your doctor may put you on an elimination diet to assist pinpoint a food allergy.
While doctors will conduct an elimination diet in diverse ways, the basics are similar: Exclude the foods you suspect are causing your symptoms, take note of how you feel, and then reintroduce the foods after several days or weeks to see if symptoms reappear.
Elimination diets should only be done in consultation with your allergist, who should recommend what to avoid and for how endless.
Never reintroduce a food you suspect as having triggered an anaphylactic reaction.
Staying on an elimination diet might lead to nutritional imbalance.
What About At-Home Testing Kits?
You may be tempted to use at-home kits that test for food allergies. If you do so, hold in mind that concerns over their accuracy own been raised, as they test for the incorrect type of antibodies (IgG instead of IgE) and are often falsely positive. This might lead you to unnecessarily avoid healthful foods.
Labs and Tests
Your medical history can assist your allergist pinpoint potential allergens and select which testing methods might be most appropriate.
These can include blood tests and skin tests. An oral food challenge may be used to confirm a diagnosis.
A prick test (also called a scratch test or a skin test) is often used to test a number of potential allergens at one time. Despite the name, this isn't a painful test, and it can provide a lot of information fairly quickly.
To act out a series of prick tests, your allergist will use either the thin skin of your forearm or your back. A drop of a solution that includes the food allergen is placed on the skin.
The allergist lightly scratches the skin to permit for a extremely minimal quantity of the solution to enter just under the surface.
If the test is positive, you'll develop a hive, or wheal (a raised white bump surrounded by a circle of itchy skin), in the area of the prick or scratch. All prick testing is done within your doctor's office under shut supervision, in case you own a serious allergic reaction.
Prick tests can provide lots of useful information, but sometimes they simply lift questions.
An inconclusive prick test will generally be followed by a more sensitive test.
Skin Prick Tests for Allergies
Blood tests are used to test for food allergies that are IgE-mediated, which are generally those with rapid onset after exposure (acute reactions), as opposed to food allergies that own delayed reactions. The name of the test is often related to the method used: for example, immunoCAP, enzyme-linked immunosorbent assay (ELISA), or radioallergosorbent (RAST) test.
To act out the test, your doctor will draw a sample of your blood.
With these tests, you never own to be exposed to the allergen directly; instead, your blood is exposed to it in the lab. A positive test result indicates that the body has produced antibodies to an allergen and is primed for a reaction.
These blood tests are precise and can assist in situations where a skin test isn't recommended—for example, to determine if a kid has outgrown a serious allergy or when a patient has severe eczema or another skin condition.
However, they do own some downsides.
They're more expensive than skin prick tests, and they take days or weeks (as opposed to minutes) to produce results.
Oral Food Challenge
In a food challenge, you ingest suspected allergens and are observed over a number of hours to determine whether you own an allergic reaction. An oral food challenge is risky and always should be carried out under shut medical supervision, but it will show the presence of an allergy conclusively.
You should never attempt an oral food challenge without consulting with your doctor since you could own a serious allergic reaction.
There are several shop-bought tests available that claim to detect allergies, but should be avoided.
- vega testing – claims to detect allergies by measuring changes in your electromagnetic field
- hair analysis – claims to detect food allergies by taking a sample of your hair and running a series of tests on it
- kinesiology testing – claims to detect food allergies by studying your muscle responses
- alternative blood tests (leukocytotoxic tests) – claim to detect food allergies by checking for the «swelling of white blood cells»
Many alternative testing kits are expensive, the scientific principles they are allegedly based on are unproven, and independent reviews own found them to be unreliable.
They should therefore be avoided.
“The only true test of whether you’re allergic to a food or not is whether you can eat it and not react to it,” said Dr. David Fleischer, an assistant professor of pediatrics at National Jewish Health. In one recent case there, doctors treated a young boy who had been given a feeding tube because blood tests indicated he was allergic to virtually every food. Food challenge testing allowed doctors to quickly reintroduce 20 foods into his diet, and they expect more to be added.
Blood tests may be unreliable because they fail to distinguish between similar proteins in diverse foods. A kid who is allergic to peanuts, for instance, might test positive for allergies to soy, green beans, peas and kidney beans.
Children with milk allergies may test positive for beef allergy.
The most significant question in diagnosing food allergy is whether the kid has tolerated the food in the past, Dr. Fleischer says. While some severe allergies are obvious, parents given a positive blood test result should seek advice from an experienced allergist who performs medically supervised food challenge testing.
Even when a food allergy has been confirmed, parents should own children retested, because numerous allergies are outgrown, particularly in the cases of milk, eggs, soy and wheat.
Doctors’ groups are also starting to acknowledge that some of their own policies may own contributed to overtesting and misdiagnoses. A committee for the American Academy of Asthma Allergy and Immunology is considering revised guidelines recommending earlier introduction of foods love eggs, peanuts and shellfish, which in the past own been delayed until age 2 or 3. A 2008 study of 10,000 British children, reported in The Journal of Allergy and Clinical Immunology, found that early exposure to peanuts lowered allergy risk.
Just as an allergy indicates oversensitivity to certain foods, it may be that doctors and parents own become oversensitive to food allergies.
In an essay in The British Medical Journal in December, Dr. Nicholas A. Christakis, a professor at Harvard Medical School, argues that an “overreaction” to allergy is leading to unnecessary testing and untrue positives.
“If the kid has been doing fine, I would advise parents not to get allergy testing, because the results are more likely to be untrue positives than true positives,” Dr. Christakis said in an interview. “If they do ponder they need allergy testing, be extremely measured and go to reputable people.”
To diagnose food allergies, your doctor first will talk to you about your reactions to certain foods and conduct a physical exam and detailed medical history.
Skin prick tests or blood tests can be used to check for reactions to specific food allergens. An oral food challenge may be done if other testing is inconclusive.
Ultimately, your doctor will use every this information to diagnose you with food allergies.
It is extremely common for people with symptoms of a food allergy to actually own a diverse condition. The suspect food may indeed be a trigger of unpleasant symptoms, but the reaction is not allergic in nature. For example, gastric reflux can be provoked by some foods, and some people own irritant reactions to boiling or spicy foods (including a runny nose).
In the case of a severe acute reaction, a food allergy might be suspected but the doctor will desire to explore whether the true allergen was instead a medication, insect sting, etc.
Food poisoning can often mimic a food allergy and should always be considered.
What is a Food Allergy? There Are Diverse Types of Allergic Reactions to Foods