Allergy test

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Allergy test
PurposeDetect allergies

Allergy testing can help confirm or rule out allergies and consequently reduce adverse reactions and limit unnecessary avoidance and medications. [1] [2]

Contents

Correct allergy diagnosis, counseling and avoidance advice based on valid allergy test results is of utmost importance and can help reduce the incidence of symptoms, need for medications and improve quality of life. [2] A healthcare provider can use the test results to identify the specific allergic triggers that may be contributing to the symptoms. Using this information, along with a physical examination and case history, the doctor can diagnose the cause of the symptoms and tailor treatments that will help the patient feel better. A negative result can help the doctor rule out allergies in order to consider other possibilities. Ruling out allergies is as important as confirming them to limit unnecessary avoidance, worry and negative social impact. [3]

Types of tests

NIH guidelines for the diagnosis and management of food allergy and the diagnosis and management of asthma recommend either allergy blood testing or skin prick testing to reliably determine allergic sensitization. [1] [4]

Blood test

For an allergy blood test, a sample of the patient's blood is sent to a laboratory for analysis. Allergy blood tests measure the presence of IgE antibodies to specific foods, pollens, mites, animals, insects and other environmental factors. (IgE, short for "immunoglobulin E", is the antibody that triggers food allergy symptoms.) The doctor looks at the test results to help determine if the patient has allergies. Allergy blood tests are not affected by antihistamine use and can be performed for people with extensive rashes that prevent using skin prick tests. For babies and young children, a single needle stick for allergy blood testing is often more gentle than several skin tests.

Skin allergy test

Skin allergy testing comprises a range of methods for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response.

Skin prick test

For a skin prick test, a patient is pricked with a series of needles that contain extracts of allergic triggers. The doctor looks for strong reactions like welts or red bumps to determine if the patient has allergies. [5] This method, although unpleasant for young children and people who dislike needle pricks, is beneficial because the person may discover an acute allergy with specially trained healthcare staff available to stop life-threatening allergic reactions such as an unexpected anaphylactic reaction. It may also allow the person to be prescribed tools for intervention needed if anaphylaxis ever occurs again, such as an mobile epinephrine pen. Epinephrine acts quickly to vasoconstrict, increasing blood flow to vital organs, and relaxing the smooth muscles in the airway, allowing the patient to breathe until emergency services arrive.

Patch test

Patch testing helps identify which substances may be causing a delayed-type allergic reaction in a patient and may identify allergens not identified by blood testing or skin prick testing. It is intended to produce a local allergic reaction on a small area of the patient's back, where the diluted chemicals were planted. The chemicals included in the patch test kit are the offenders in approximately 85–90 percent of contact allergic eczema and include chemicals present in metals (e.g., nickel), rubber, leather, formaldehyde, lanolin, fragrance, toiletries, hair dyes, medicine, pharmaceutical items, food, drink, preservative, and other additives.

Related Research Articles

Allergy Immune system response to a substance that most people tolerate well

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling. Food intolerances and food poisoning are separate conditions.

An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.

Anaphylaxis Life-threatening allergic reaction

Anaphylaxis, often known as anaphylactic shock, is a serious allergic reaction that is rapid in onset and may cause death. It typically causes more than one of the following: an itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness and low blood pressure. These symptoms typically come on over minutes to hours.

Allergic rhinitis Human disease

Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, itchy, and watery eyes, and swelling around the eyes. The fluid from the nose is usually clear. Symptom onset is often within minutes following allergen exposure, and can affect sleep and the ability to work or study. Some people may develop symptoms only during specific times of the year, often as a result of pollen exposure. Many people with allergic rhinitis also have asthma, allergic conjunctivitis, or atopic dermatitis.

A radioallergosorbent test (RAST) is a blood test using radioimmunoassay test to detect specific IgE antibodies in order to determine the substances a subject is allergic to. This is different from a skin allergy test, which determines allergy by the reaction of a person's skin to different substances.

Food allergy Hypersensitivity reaction to a food

A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure. This typically occurs within minutes to several hours of exposure. When the symptoms are severe, it is known as anaphylaxis. A food intolerance and food poisoning are separate conditions, not due to an immune response.

Type I hypersensitivity Medical condition

Type I hypersensitivity is an allergic reaction provoked by re-exposure to a specific type of antigen referred to as an allergen. Type I is distinct from type II, type III and type IV hypersensitivities.

Food intolerance is a detrimental reaction, often delayed, to a food, beverage, food additive, or compound found in foods that produces symptoms in one or more body organs and systems, but generally refers to reactions other than food allergy. Food hypersensitivity is used to refer broadly to both food intolerances and food allergies.

Peanut allergy Type of food allergy caused by peanuts

Peanut allergy is a type of food allergy to peanuts. It is different from tree nut allergies, because peanuts are legumes and not true nuts. Physical symptoms of allergic reaction can include itchiness, hives, swelling, eczema, sneezing, asthma attack, abdominal pain, drop in blood pressure, diarrhea, and cardiac arrest. Anaphylaxis may occur. Those with a history of asthma are more likely to be severely affected.

Soy allergy Medical condition

Soy allergy is a type of food allergy. It is a hypersensitivity to ingesting compounds in soy, causing an overreaction of the immune system, typically with physical symptoms, such as gastrointestinal discomfort, respiratory distress, or a skin reaction. Soy is among the eight most common foods inducing allergic reactions in children and adults. It has a prevalence of about 0.3% in the general population.

Oral allergy syndrome (OAS) is a type of food allergy classified by a cluster of allergic reactions in the mouth and throat in response to eating certain fruits, nuts, and vegetables that typically develops in adults with hay fever.

Milk allergy Type of food allergy caused by milk

Milk allergy is an adverse immune reaction to one or more proteins in cow's milk. When allergy symptoms occur, they can occur rapidly or have a gradual onset. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine among other measures. The latter can take hours to days to appear, with symptoms including atopic dermatitis, inflammation of the esophagus, enteropathy involving the small intestine and proctocolitis involving the rectum and colon.

Egg allergy Immune hypersensitivity to proteins found in eggs

Egg allergy is an immune hypersensitivity to proteins found in chicken eggs, and possibly goose, duck, or turkey eggs. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus.

Wheat allergy Medical condition

Wheat allergy is an allergy to wheat which typically presents itself as a food allergy, but can also be a contact allergy resulting from occupational exposure. Like all allergies, wheat allergy involves immunoglobulin E and mast cell response. Typically the allergy is limited to the seed storage proteins of wheat. Some reactions are restricted to wheat proteins, while others can react across many varieties of seeds and other plant tissues. Wheat allergy is rare. Prevalence in adults was found to be 0.21% in a 2012 study in Japan.

Skin allergy testing comprises a range of methods for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response.

Food Protein-Induced Enterocolitis Syndrome (FPIES) is a systemic, non IgE-mediated response to a specific trigger within food - most likely food protein. FPIES presents in two different forms: an acute form and a chronic form. In its acute form, FPIES presents with vomiting that usually begins 1 to 4 hours after trigger food ingestion. Vomiting is often followed by a paleness to the skin, lethargy, and potentially watery, perhaps blood-tinged diarrhea. In the severe form of acute FPIES, a person will vomit until dehydration and until a shock-like state, which occurs in 15% of patients. In its chronic form, which can be difficult to diagnose until a person has already met diagnostic criteria for acute FPIES, after repeated or regular ingestion of the trigger food, the person presents with chronic or episodic vomiting, failure to thrive, and watery, perhaps blood-tinged diarrhea. FPIES can potentially develop at any age but seems most commonly to develop within the first few years of life. FPIES has mainly been documented in young infants, but can exist in older children and adults. Some people develop both FPIES and an IgE-mediated type of reaction to the same food, and having FPIES can increase a person's risk of also developing IgE-mediated food allergies.

Alcohol-induced respiratory reactions, also termed alcohol-induced asthma and alcohol-induced respiratory symptoms, are increasingly recognized as a pathological bronchoconstriction response to the consumption of alcohol that afflicts many people with a "classical" form of asthma, the airway constriction disease evoked by the inhalation of allergens. Alcohol-induced respiratory reactions reflect the operation of different and often racially related mechanisms that differ from those of classical, allergen-induced asthma.

Rice allergy is a type of food allergy. People allergic to rice react to some rice proteins after they eat rice or breathe in rice steam. Although some reactions might lead to severe health problems, doctors can diagnose rice allergy with many methods and help allergic people to avoid reactions.

Fish allergy Food allergy triggered by fish

Fish allergy is an immune hypersensitivity to proteins found in fish. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus. Fish is one of the eight common food allergens, responsible for 90% of allergic reactions to foods: cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, and soy beans.

Shellfish allergy Medical condition

Shellfish allergy is among the most common food allergies. "Shellfish" is a colloquial and fisheries term for aquatic invertebrates used as food, including various species of molluscs such as clams, mussels, oysters and scallops, crustaceans such as shrimp, lobsters and crabs, and cephalopods such as squid and octopus. Shellfish allergy is an immune hypersensitivity to proteins found in shellfish. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus. Shellfish is one of the eight common food allergens, responsible for 90% of allergic reactions to foods: cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, and soy beans.

References

  1. 1 2 Boyce, J et al., "Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of NIAID-Sponsored Expert Panel", J Allergy Clin Immunol 2010; 126: S1–S58.
  2. 1 2 National Institute for Health and Care Excellence, "Diagnosis and assessment of food allergy in children and young people in primary care and community settings", 2011. Retrieved 26 December 2019.
  3. Sampson, H et al., "Utility of food-specific IgE concentrations in predicting symptomatic food allergy", J Allergy Clin Immunol 2001; 107: 891–6.
  4. "NIH Guidelines for the Diagnosis and Management of Food Allergy in the United States. Report of the NIAID-Sponsored Expert Panel", 2010, NIH Publication no. 11-7700.
  5. Asthma and Allergy Foundation of America, "Skin Testing for Allergies", 25 June 2012. Retrieved January 2013.