Allergy blood test what is tested
Your kid may need to avoid taking certain medicines before the tests because they might affect the test result. For example, your kid may need to stop taking any antihistamines one to several days before the tests. Make certain the healthcare provider knows about any medicines, herbs, or supplements that your kid takes. Your kid should not stop using any regular medicines without first consulting with your healthcare provider.
What is an allergy blood test?
Allergies are a common and chronic condition that involves the body’s immune system.
Normally, your immune system works to fight off viruses, bacteria, and other infectious agents. When you own an allergy, your immune system treats a harmless substance, love dust or pollen, as a threat. To fight this perceived threat, your immune system makes antibodies called immunoglobulin E (IgE).
Substances that cause an allergic reaction are called allergens. Besides dust and pollen, other common allergens include animal dander, foods, including nuts and shellfish, and certain medicines, such as penicillin. Allergy symptoms can range from sneezing and a stuffy nose to a life-threatening complication called anaphylactic shock.
Allergy blood tests measure the quantity of IgE antibodies in the blood. A little quantity of IgE antibodies is normal. A larger quantity of IgE may mean you own an allergy.
Other names: IgE allergy test, Quantitative IgE, Immunoglobulin E, Entire IgE, Specific IgE
Testing for IgE antibodies may be useful to establish the diagnosis of an allergic disease and to define the allergens responsible for eliciting signs and symptoms.
Testing also may be useful to identify allergens which may be responsible for allergic disease and/or anaphylactic episode, to confirm sensitization to specific allergens prior to beginning immunotherapy, and to investigate the specificity of allergic reactions to insect venom allergens, drugs, or chemical allergens.
Clinical manifestations of immediate hypersensitivity (allergic) diseases are caused by the release of proinflammatory mediators (histamine, leukotrienes, and prostaglandins) from immunoglobulin E (IgE)-sensitized effector cells (mast cells and basophils) when cell-bound IgE antibodies interact with allergen.
In vitro serum testing for IgE antibodies provides an indication of the immune response to allergen(s) that may be associated with allergic disease.
The allergens chosen for testing often depend upon the age of the patient, history of allergen exposure, season of the year, and clinical manifestations.
In individuals predisposed to develop allergic disease(s), the sequence of sensitization and clinical manifestations proceed as follows: eczema and respiratory disease (rhinitis and bronchospasm) in infants and children less than 5 years due to food sensitivity (milk, egg, soy, and wheat proteins) followed by respiratory disease (rhinitis and asthma) in older children and adults due to sensitivity to inhalant allergens (dust mite, mold, and pollen inhalants).
Detection of IgE antibodies in serum (Class 1 or greater) indicates an increased likelihood of allergic disease as opposed to other etiologies and defines the allergens that may be responsible for eliciting signs and symptoms.
The level of IgE antibodies in serum varies directly with the concentration of IgE antibodies expressed as a class score or kU/L.
Testing for IgE antibodies is not useful in patients previously treated with immunotherapy to determine if residual clinical sensitivity exists, or in patients in whom the medical management does not depend upon identification of allergen specificity.
Some individuals with clinically insignificant sensitivity to allergens may own measurable levels of IgE antibodies in serum, and results must be interpreted in the clinical context.
False-positive results for IgE antibodies may happen in patients with markedly elevated serum IgE (>2,500 kU/L) due to nonspecific binding to allergen solid phases.
Homburger HA: Chapter 53: Allergic diseases.
In Clinical Diagnosis and Management by Laboratory Methods. 21st edition. Edited by RA McPherson, MR Pincus. WB Saunders Company, New York, 2007, Part VI, pp 961-971
What is food allergy testing?
Food allergy testing is a way to check the body’s reaction to certain foods. One or more of the following tests may be done:
- blood test
- food challenge test
- skin prick test
- elimination diet.
Special InstructionsLibrary of PDFs including pertinent information and forms related to the test
Frequently Asked Questions about Food Protein-Induced Enterocolitis Syndrome (FPIES)
How Do You Treat an FPIES Reaction?
Always follow your doctor’s emergency plan pertaining to your specific situation.
Rapid dehydration and shock are medical emergencies. If your kid is experiencing symptoms of FPIES or shock, immediately contact your local emergency services (9-1-1). If you are uncertain if your kid is in need of emergency services, contact 9-1-1 or your physician for guidance. The most critical treatment during an FPIES reaction is intravenous (IV) fluids, because of the risk and prevalence of dehydration. Children experiencing more severe symptoms may also need steroids and in-hospital monitoring.
Mild reactions may be capable to be treated at home with oral electrolyte re-hydration (e.g., Pedialyte®).
How is FPIES Diagnosed?
FPIES is hard to diagnose, unless the reaction has happened more than once, as it is diagnosed by symptom presentation. Typically, foods that trigger FPIES reactions are negative with standard skin and blood allergy tests (SPT, RAST) because they glance for IgE-mediated responses. However, as stated before, FPIES is not IgE-mediated.
Atopy patch testing (APT) is being studied for its effectiveness in diagnosing FPIES, as well as predicting if the problem food is no longer a trigger.
Thus, the outcome of APT may determine if the kid is a potential candidate for an oral food challenge (OFC). APT involves placing the trigger food in a metal cap, which is left on the skin for 48 hours. The skin is then watched for symptoms in the following days after removal. Please consult your child’s doctor to discuss if APT is indicated in your situation.
Does FPIES Require Epinephrine?
Not generally, because epinephrine reverses IgE-mediated symptoms, and FPIES is not IgE-mediated.
Based on the patient’s history, some doctors might prescribe epinephrine to reverse specific symptoms of shock (e.g., low blood pressure). However, this is only prescribed in specific cases.
How Do You Care for a Kid With FPIES?
Treatment varies, depending on the patient and his/her specific reactions. Often, infants who own reacted to both dairy and soy formulas will be placed on hypoallergenic or elemental formula.
Some children do well breastfeeding. Other children who own fewer triggers may just strictly avoid the offending food(s).
New foods are generally introduced extremely slowly, one food at a time, for an extended period of time per food. Some doctors recommend trialing a single food for up to three weeks before introducing another.
Because it’s a rare, but serious condition, in the event of an emergency, it is vital to get the correct treatment. Some doctors provide their patients with a letter containing a brief description of FPIES and its proper treatment. In the event of a reaction, this letter can be taken to the ER with the child.
What Does FPIES Stand For?
FPIES is Food Protein-Induced Enterocolitis Syndrome.
It is commonly pronounced «F-Pies», as in «apple pies», though some physicians may refer to it as FIES (pronounced «fees», considering food-protein as one word). Enterocolitis is inflammation involving both the little intestine and the colon (large intestine).
How Do I know If My Kid Has Outgrown FPIES?
Together with your child’s doctor, you should determine if/when it is likely that your kid may own outgrown any triggers. Obviously, determining if a kid has outgrown a trigger is something that needs to be evaluated on a food-by-food basis. As stated earlier, APT testing may be an option to assess oral challenge readiness.
Another factor for you and your doctor to consider is if your kid would physically be capable to handle a possible failed challenge.
When the time comes to orally challenge an FPIES trigger, most doctors familiar with FPIES will desire to schedule an in-office food challenge. Some doctors (especially those not practicing in a hospital clinic setting) may select to challenge in the hospital, with an IV already in put, in case of emergency. Each doctor may own his or her own protocol, but an FPIES trigger is something you should definitely NOT challenge without discussing thoroughly with your doctor.
Be aware that if a kid passes the in-office portion of the challenge, it does not mean this food is automatically guaranteed «safe.» If a child’s delay in reaction is fairly short, a kid may fail an FPIES food challenge while still at the office/hospital.
For those with longer reaction times, it may not be until later that day that symptoms manifest. Some may react up to three days later. Delay times may vary by food as well. If a kid has FPIES to multiple foods, one food may trigger symptoms within four hours; a diverse food may not trigger symptoms until six or eight hours after ingestion.
What is Shock and What are the Symptoms?
Shock is a life-threatening condition. Shock may develop as the result of sudden illness, injury, or bleeding. When the body cannot get enough blood to the vital organs, it goes into shock.
Signs of shock include:
Weakness, dizziness, and fainting.
Cool, pale, clammy skin.
Weak, quick pulse.
Shallow, quick breathing.
Low blood pressure.
Extreme thirst, nausea, or vomiting.
Confusion or anxiety.
What is a Typical FPIES Reaction?
As with every things, each kid is diverse, and the range, severity and duration of symptoms may vary from reaction to reaction.
Unlike traditional IgE-mediated allergies, FPIES reactions do not manifest with itching, hives, swelling, coughing or wheezing, etc. Symptoms typically only involve the gastrointestinal system, and other body organs are not involved. FPIES reactions almost always start with delayed onset vomiting (usually two hours after ingestion, sometimes as tardy as eight hours after). Symptoms can range from mild (an increase in reflux and several days of runny stools) to life threatening (shock). In severe cases, after repeatedly vomiting, children often start vomiting bile. Commonly, diarrhea follows and can final up to several days. In the worst reactions (about 20% of the time), the kid has such severe vomiting and diarrhea that s/he rapidly becomes seriously dehydrated and may go into shock.
Is FPIES A Lifelong Condition?
Numerous children outgrow FPIES by about age three. Note, however, that the time varies per individual and the offending food, so statistics are a guide, but not an absolute. In one study, 100% of children with FPIES reactions to barley had outgrown and were tolerating barley by age three. However, only 40% of those with FPIES to rice, and 60% to dairy tolerated it by the same age.
What are Some Common FPIES Triggers?
The most common FPIES triggers are traditional first foods, such as dairy and soy. Other common triggers are rice, oat, barley, green beans, peas, sweet potatoes, squash, chicken and turkey. A reaction to one common food does not mean that every of the common foods will be an issue, but patients are often advised to proceed with caution with those foods.
Note that while the above foods are the most prevalent, they are not exclusive triggers. Any food has the potential to trigger an FPIES reaction. Even trace amounts can cause a reaction.
What is FPIES?
FPIES is a non-IgE mediated immune reaction in the gastrointestinal system to one or more specific foods, commonly characterized by profuse vomiting and diarrhea. FPIES is presumed to be cell mediated. Poor growth may happen with continual ingestion. Upon removing the problem food(s), every FPIES symptoms subside. (Note: Having FPIES does not preclude one from having other allergies/intolerances with the food.) The most common FPIES triggers are cow’s milk (dairy) and soy.
However, any food can cause an FPIES reaction, even those not commonly considered allergens, such as rice, oat and barley.
A kid with FPIES may experience what appears to be a severe stomach bug, but the «bug» only starts a couple hours after the offending food is given. Numerous FPIES parents own rushed their children to the ER, limp from extreme, repeated projectile vomiting, only to be told, «It’s the stomach flu.» However, the next time they feed their children the same solids, the dramatic symptoms return.
When Do FPIES Reactions Occur?
FPIES reactions often show up in the first weeks or months of life, or at an older age for the exclusively breastfed kid.
Reactions generally happen upon introducing first solid foods, such as baby cereals or formulas, which are typically made with dairy or soy. (Infant formulas are considered solids for FPIES purposes.) While a kid may own allergies and intolerances to food proteins they are exposed to through breastmilk, FPIES reactions generally don’t happen from breastmilk, regardless of the mother’s diet. An FPIES reaction typically takes put when the kid has directly ingested the trigger food(s).
What Does IgE vs Cell Mediated Mean?
IgE stands for Immunoglobulin E. It is a type of antibody, formed to protect the body from infection, that functions in allergic reactions.
IgE-mediated reactions are considered immediate hypersensitivity immune system reactions, while cell mediated reactions are considered delayed hypersensitivity. Antibodies are not involved in cell mediated reactions. For the purpose of understanding FPIES, you can disregard every you know about IgE-mediated reactions.
How is FPIES Diverse From MSPI, MSPIES, MPIES, Etc.?
MPIES (milk-protein induced enterocolitis syndrome) is FPIES to cow’s milk only.
MSPIES (milk- and soy-protein induced enterocolitis syndrome) is FPIES to milk and soy. Some doctors do create these subdivisions, while others declare that milk and soy are simply the two most common FPIES triggers and give the diagnosis of «FPIES to milk and/or soy.»
MSPI is milk and soy protein intolerance. Symptoms are those of allergic colitis and can include colic, vomiting, diarrhea and blood in stools. These reactions are not as severe or immediate as an FPIES reaction.
Fogg MI, Brown-Whitehorn TA, Pawlowski NA, Spergel JM. (2006). Atopy Patch Test for the Diagnosis of Food Protein-Induced Enterocolitis Syndrome.
Pediatric Allergy and Immunology 17: 351–355. Retrieved on December 31, 2007 from http://pediatrics.aappublications.org/cgi/content/abstract/120/Supplement_3/S116.
Burks, AW. (2006). Don’t Feed Her That! Diagnosing and Managing Pediatric Food Allergy. Pediatric Basics. Gerber Products Company: 115. Retrieved on December 31, 2007 from http://www.gerber.com/content/usa/html/pages/pediatricbasics/articles/115_01-dontfeed.html.
Moore, D. Food Protein-Induced Enterocolitis Syndrome. (2007, April 11). Retrieved on December 31, 2007 from http://allergies.about.com/od/foodallergies/a/fpies.htm.
(2005). Food Protein-Induced Enterocolitis Syndrome: Case Presentations and Management Lessons. Journal of Allergy and Clinical Immunology Vol. 115, 1:149-156. Retrieved on December 31, 2007 from http://www.jacionline.org/article/PIIS0091674904024881/fulltext.
Nowak-Wegrzyn, A., Sampson, HA, Wood, RA, Sicherer, SH.
MD, Robert A. Wood, MD and Scott H. Sicherer, MD. (2003). Food Protein-Induced Enterocolitis Syndrome Caused by Solid Food Proteins. Pediatrics. Vol. 111.
4: 829-835. Retrieved on December 31, 2007 from http://pediatrics.aappublications.org/cgi/content/full/111/4/829#T1.
Nocerino, A., Guandalini, S. (2006, April 11).
Protein Intolerance. Retrieved on December 31, 2007 from http://www.emedicine.com/ped/topic1908.htm. WebMD Medical Reference from Healthwise. (2006, May 31). Shock, Topic Overview. Retrieved on December 31, 2007 from http://www.webmd.com/a-to-z-guides/shock-topic-overview.
American Academy of Allergy, Asthma and Immunology. (2007). Tips to Remember: What is an Allergic Reaction? Retrieved on December 31, 2007 from http://www.aaaai.org/patients/publicedmat/tips/whatisallergicreaction.stm.
(2006). Understanding and Managing Your Child’s Food Allergies. A Johns Hopkins Press Health Book. 336.
Medical Review February 2008.
Why is it done?
If your kid has a history of allergic symptoms after eating certain foods, your healthcare provider may recommend that your kid own tests to check for food allergies. This will assist you know which foods your kid should avoid eating to prevent an allergic reaction.
A extremely few foods are responsible for most food allergies. The most common foods that cause allergies are milk, soy, eggs, peanuts, tree nuts, fish, shellfish, and wheat.
Your kid may need to be tested for food allergies if your kid has some of the following symptoms shortly after eating:
- swelling of the lips or eyelids
- throat tightness
- wheezing or other breathing trouble
- stomach cramps, vomiting or diarrhea
- redness of the skin
If possible, see your healthcare provider while the allergic reaction is occurring.
This will assist your provider with the diagnosis.
How are the tests done?
Your healthcare provider or allergist may desire to do one or more of the following tests:
Skin prick tests: A skin prick test is often used to test for food allergies. For this test, a drop of food extract is put on the skin and then the skin is pricked with a little needle through the drop of the food extract.
The test can also be done with a pricking device that has been presoaked in the food extract. Only the top layer of skin is pricked. The test is generally done on the child’s back or arm. The skin test is ready to check in about 15 minutes. If your kid is allergic to one of the foods, a red bump that looks love a mosquito bite will appear at the spot where the food extract was placed.
Intradermal skin test: For this test, a little quantity of allergen is injected under the skin with a syringe. This test is more sensitive than the skin prick method, and can be used if the skin prick tests are negative.
Skin tests are not extremely painful, but they can be scary to a young kid.
Before the test, explain to your kid what is going to happen to assist calm any fears. For children who own extremely severe allergic reactions or other skin conditions such as eczema, the skin test may cause irritation or even life-threatening reactions. In this case, the RAST Test would be a safe alternative.
Blood test (RAST test): Blood tests are not done as often as skin prick tests, but they can be useful in certain cases.
Blood tests are sometimes done on babies less than 1 year ancient because their skin does not react to the prick test as well as it does for older children. The test measures the quantity of IgE antibody in the blood. The body makes this type of antibody when trying to fight off the allergy-causing substances in food (allergens). A sample of your child’s blood is sent to a lab for testing. The test results show whether your childâ€™s body is making antibodies to these foods and thus whether your kid is allergic to these foods.
Food challenge: A food challenge test is considered to be the most dependable way to test for food allergies. The test is generally done in your providerâ€™s office. Sometimes it is done in the hospital. During this test, your kid is given gradually increasing amounts of the food while a healthcare provider watches for symptoms. This test should be done only by a trained professional who is ready to treat your kid in case of a serious reaction. In cases of allergies that cannot be tested using a blood test (such as some gastrointestinal allergies), a food challenge test may be the only excellent way to make a diagnosis.
The food challenge is also excellent way to see if your kid has outgrown an allergy.
Elimination diet: Your healthcare provider may desire your kid to stop eating suspect foods for a week or two and then add the items back into the diet one at a time. This can assist join symptoms to specific foods. During this time, you will need to hold a record of any symptoms your kid has and the foods he eats. If your kid has had a severe reaction to foods, this method cannot be used.