What does equivocal allergy test result mean

Application of the patch tests takes about half an hour, though numerous times the overall appointment time is longer as the provider will take an extensive history. Tiny quantities of 25 to ~150 materials (allergens) in individual square plastic or circular aluminium chambers are applied to the upper back. They are kept in put with special hypoallergenic adhesive tape. The patches stay in put undisturbed for at least 48 hours. Vigorous exercise or stretching may disrupt the test.

At the second appointment, generally 48 hours later, the patches are removed.

Sometimes additional patches are applied. The back is marked with an indelible black felt tip pen or other suitable marker to identify the test sites, and a preliminary reading is done. These marks must be visible at the third appointment, generally 24–48 hours later (72–96 hours after application). In some cases, a reading at 7 days may be requested, especially if a special metal series is tested.


Common allergens

The top allergens from 2005–06 were: nickel sulfate (19.0%), Myroxylon pereirae (Balsam of Peru, 11.9%), perfume stir I (11.5%), quaternium-15 (10.3%), neomycin (10.0%), bacitracin (9.2%), formaldehyde (9.0%), cobalt chloride (8.4%), methyldibromoglutaronitrile/phenoxyethanol (5.8%), p-phenylenediamine (5.0%), potassium dichromate (4.8%), carba stir (3.9%), thiuram stir (3.9%), diazolidinyl urea (3.7%), and 2-bromo-2-nitropropane-1,3-diol (3.4%).[1]

The most frequent allergen recorded in numerous research studies around the world is nickel.

Nickel allergy is more prevalent in young women, and is especially associated with ear piercing or any nickel-containing watch, belt, zipper, or jewelry. Other common allergens are surveyed in North America by the North American Contact Dermatitis Group (NACDG).[1]


Food allergy

Dermatologists may refer a patient with a suspected food allergy for patch testing.[2] Foods identified by blood testing or skin prick testing may or may not overlap with foods identified by patch testing.[2]

Certain food additives and flavorings can cause allergic reactions around and in the mouth, around the anus and vulva as food allergens pass out of the body, or cause a widespread rash on the skin.

Allergens such as nickel, Balsam of Peru, parabens, sodium benzoate, or cinnamic aldehyde may worsen or cause skin rashes.

Foods that cause urticaria (hives) or anaphylaxis (such as peanuts) cause a type I hypersensitivity reaction whereby the part of the food molecule is directly recognized by cells shut to the skin, called mast cells. Mast cells own antibodies on their surface called immunoglobulin E (IgE). These act as receptors, and if they recognize the allergen, they release their contents, causing an immediate allergic reaction. Type I reactions love anaphylaxis are immediate and do not take 2 to 4 days to appear.

In a study of patients with chronic hives who were patch tested, those who were found allergic and avoided every contact with their allergen, including dietary intake, stopped having hives.

Those who started eating their allergen again had recurrence of their hives.[3]


References

  • ^ ab«Food Allergy Center». Massgeneral.org. April 22, 2009. Retrieved April 6, 2014.
  • ^ abZug KA, Warshaw EM, Fowler JF Jr, Maibach HI, Belsito DL, Pratt MD, Sasseville D, Storrs FJ, Taylor JS, Mathias CG, Deleo VA, Rietschel RL, Marks J. Patch-test results of the North American Contact Dermatitis Group 2005–2006. Dermatitis.

    2009 May–Jun;20(3):149-60.

  • ^Guerra L, Rogkakou A, Massacane P, Gamalero C, Compalati E, Zanella C, Scordamaglia A, Canonica WG, Passalacqua G. Role of contact sensitization in chronic urticaria. J Am Acad Dermatol 2007; 56:88–90.


Mechanism

A patch test relies on the principle of a type IV hypersensitivity reaction.

The first step in becoming allergic is sensitization. When skin is exposed to an allergen, the antigen-presenting cells (APCs) – also known as Langerhans cell or Dermal Dendritic Cell – phagocytize the substance, break it below to smaller components and present them on their surface bound major histocompatibility complicated type two (MHC-II) molecules.

The APC then travels to a lymph node, where it presents the displayed allergen to a CD4+ T-cell, or T-helper cell. The T-cell undergoes clonal expansion and some clones of the newly formed antigen specific sensitized T-cells travel back to the site of antigen exposure.

When the skin is again exposed to the antigen, the memory t-cells in the skin recognize the antigen and produce cytokines (chemical signals), which cause more T-cells to migrate from blood vessels.

This starts a complicated immune cascade leading to skin inflammation, itching, and the typical rash of contact dermatitis.

In general, it takes 2–4 days for a response in patch testing to develop. The patch test is just induction of a contact dermatitis in a little area.


Food Allergy Challenge Testing

Foods can cause numerous diverse types of allergic symptoms. Some persons experience gastrointestinal problems such as cramping, constipation or diarrhea. Other persons suffer from skin rashes (hives or eczema). Less commonly, some may experience serious life-threatening reactions such as: asthma, throat closing or loss of consciousness.

A food that causes allergic symptoms generally causes similar symptoms on each repeated exposure, provided that the same quantity of food is eaten each time (rarely symptoms can be more severe). Some persons are allergic only to raw foods while others are allergic only to cooked foods. (Most persons will react to both). Extremely little amounts of foods may trigger allergic reactions and as a result, are often hard to identify.

Food allergy symptoms can be immediate; generally beginning within 2 hrs. of ingestion, or delayed; in which symptoms which may not develop for up to 72 hrs.

«Immediate» food allergies are suspected when allergic antibodies (IgE) are detected in the blood by laboratory RAST testing or by skin prick testing. The presence of allergic antibodies to foods alone is generally not sufficient to diagnose a food allergy. The confirmation of food allergy often requires challenge testing. Challenge testing is performed only in situations in which a food is suspected of causing non-life threatening symptoms. If a food were strongly suspected of causing dizziness, throat swelling, (body tissue swelling) or shortness of breath, then challenge testing would not generally be recommended.

RAST testing reports the presence of allergic antibodies in the blood.

Typically they are given numerical scores/classes (0 to 6). Class 0-1 is called «equivocal» and is rarely if ever significant. The higher the RAST class/score, the more likely it is that a true food allergy exists. Challenge testing should start with the highest-RAST class foods and continue until all positive foods own been tested. Allergy symptoms that repeatedly develop after challenge testing with a food confirms sensitivity (allergy) and the lack of allergic symptoms generally disproves allergy. Not every RAST or skin test positive foods will cause allergy symptoms. Foods that are RAST or skin test negative rarely if ever cause immediate allergy symptoms.

To be absolutely certain no allergy exists, challenge testing is occasionally recommended when skin testing and/or RAST testing is negative. (Challenge testing to RAST or skin test negative foods is generally not necessary).

Childhood eczema is the most common disease in which challenge testing is used to confirm food allergy. If eczema is the only allergic symptom thought to be triggered by foods, it is generally extremely safe to act out food challenge testing and this can be done at home.

Challenge testing is often recommended when multiple foods are noted to own stimulated allergic antibodies to determine which of the foods are most likely to be causing the allergic symptoms. If serious allergic symptoms are possibly due to a food (but unlikely) (i.e. no allergic antibodies can be detected), challenge testing may occasionally be recommended, but this should be done only in a safer environment such as a hospital ER waiting room.

Again it must be stressed that if testing has detected allergic antibodies to a food and serious allergic symptoms are likely to own occurred following ingestion, avoidance is the only safe recommendation.

Before challenge testing is done, every suspected foods are generally eliminated from the diet for at least 2 weeks (or at least those foods with a RAST class 2 or greater score).

Selecting only RAST test negative foods to eat is the «best» way to develop an elimination diet. Anti-histamine use should be stopped at least 5 days before challenge testing. Food challenges are done with only one food at a time. The food should be eaten slowly over a one hour time period and only water should be used as a drink. The largest quantity of the food that is ever generally eaten should be consumed (i.e. a normal portion). No other foods should be given for 3 hours and no additional foods suspected of causing allergy (RAST positive foods) should be eaten for at least two days to observe for the development of any «delayed» allergic symptoms.

If allergic symptoms develop at any time during the challenge test, the allergy medications contained in the key chain carrier that we own provided to you should be taken. The Epi-pen is used for severe life-threatening symptoms such as throat closing, severe cough (possible asthma), wheezing, shortness of breath or dizziness/passing out. If an Epi-pen is ever used you should call 911 immediately after.

If allergic symptoms are thought to happen following a challenge test, repeating this challenge on another day may be necessary to be certain it has caused the problem. In children, finish avoidance of any food proved to be causing allergic symptoms should continue for at least 2 years before re-exposure is attempted.

Peanut, tree nuts, egg and seafood allergies are less likely to be ever «out-grown.» Food allergies in adults do not typically ever «go away.» If you do not understand challenge testing after reading this instruction sheet please call 499-0033 for further clarification before beginning. Never act out a challenge test on any food suspected of causing allergic reactions without a doctor’s approval.

Drs. Michael & Adrianne Vaughn

What Is Food Allergy Testing?

You may be asked to undergo some allergy testing. Your allergist-immunologist may employ skin testing, in which a diluted quantity of the appropriate food extract is placed on the skin and the skin is then lightly punctured.

This procedure is safe and generally not painful. Within 15 to 20 minutes, a positive reaction typically appears as a raised bump surrounded by redness, similar to a mosquito bite, and indicates the presence of allergic, or IgE, antibodies to the specific food. In some cases, an allergy (IgE) blood test can be used to provide similar information to that obtained by the skin test. The IgE blood test is generally more expensive than skin testing and the results are generally not available for one to two weeks.

If properly performed and interpreted, skin tests or IgE blood tests to foods are dependable and excellent screening tests for food allergy. However, it’s entirely possible to test «allergic» to a food (by skin testing or IgE blood testing) and yet own no symptoms when that food is eaten.

Thus, confirmation requires appropriately designed oral challenge testing with each suspected food.

How Do Allergists Determine Which Foods Make Me Sick?

Some people know exactly what food causes their allergic symptoms. They eat peanuts or a peanut-containing product and immediately break out with hives. Other individuals need their allergist’s assist in determining the «culprit», especially when the specific food cannot be identified or when the symptoms show up numerous hours after ingesting an offending food.

Your allergist-immunologist will typically start by taking a comprehensive medical history.

Specifically, you’ll be asked about the symptoms you experience following the food ingestion, how endless after the food ingestion they occurred, how much of the offending food was ingested, how often the reaction has occurred and what type of medical treatment, if any, was required. Moreover, you will be asked about your overall diet, your family’s medical history and your home environment.

These questions are necessary because your allergist wants to eliminate the possibility that another problem or allergic condition may be causing or adding to your symptoms. For example, a patient’s allergy to inhalant pollen such as ragweed may be related to allergic symptoms in the mouth and throat following the ingestion of certain melons, such as watermelon, cantaloupe or honeydew.

What Causes my Symptoms?

A food allergy is the result of your body’s immune system overreacting to food proteins called allergens.

Normally, your immune system and defense mechanisms hold you healthy by fighting off infections and inactivating proteins such as food allergens, which could potentially cause allergic reactions. Therefore, the majority of people develop a tolerance to a wide variety of diverse foods in their diet.

In the individual with food allergy, the immune system produces increased amounts of immunoglobulin E antibody, or IgE. When these antibodies battle with food allergens, histamine and other chemicals are released as part of the body’s immune reaction to these substances. These chemicals can cause blood vessels to widen, smooth muscles to contract, and affected skin areas to become red, itchy and swollen.

These IgE antibodies can be found in diverse body tissues — skin, intestines and lungs — where specific allergy symptoms, such as hives, vomiting, diarrhea and wheezing are observed.

Not every adverse reactions to foods are due to allergy. Some reactions to cow’s milk, for example, are related to a deficiency of an enzyme (lactase) that normally breaks below a sugar in milk (lactose). When individuals with lactase deficiency drink cow’s milk or eat other dairy products, they may experience intestinal symptoms, including stomach cramping, gas and diarrhea. This is sometimes misinterpreted as a food allergy.

How Do Special Diets Assist Pinpoint the Problem?

With the information gained from your history, physical exam and testing, your allergist may further narrow below the suspected foods by placing you on a special diet.

If your symptoms happen only occasionally, the culprit is likely a food that is eaten infrequently. Your allergist-immunologist may enquire you to hold a daily food diary listing every food and medication ingested, along with your symptoms for the day. By reviewing and comparing «good days» with «bad days», you and your allergist may be capable to determine which food is causing your reaction.

If only one or two foods seem to be causing allergic reactions, it may be necessary for the patient to go on a food elimination diet.

The suspect food must be completely eliminated in any form for a short time — one to two weeks. If the allergic symptoms subside during abstinence and flare up when the food is ingested again, the likelihood of identifying the problem food can be increased.

If several foods appear to cause problems and/or the diagnosis of food allergy is equivocal, your allergist may desire to confirm the role of each suspected food by oral food challenge testing.

Not every positive skin tests and/or IgE blood tests equal a definite food allergy. With this in mind, food challenges are the best way to determine whether or not a food allergy really exists.

During an oral food challenge test the patient will eat or drink little portions of a suspected food in gradually increasing portions over a given period of time, generally under a physician’s supervision, to see if an allergic reaction occurs.

Why Me?

Why Own I Developed Food Allergy?

Heredity seems to be the prime reason some people own allergies and others don’t. If both your parents own allergies, you own approximately a 75 percent chance of being allergic. If one parent is allergic, or you own relatives on one side with allergies, you own a 30 percent to 40 percent chance of developing some form of allergy. If neither parent has apparent allergy, the chance is 10 percent to 15 percent.

Although food allergy occurs most often in infants and children, it can appear at any age and can be caused by foods that had been previously eaten without any problems.

Finally, excessive exposure to a specific food may affect the overall rate of allergy to that food, as testified to by the high prevalence of fish allergy among Scandinavians and of rice allergy among the Japanese.

Which Foods Are Most Likely To Cause Allergy?

Eggs, cows milk, peanuts, soy, wheat, tree nuts, fish and shellfish are the most common foods causing allergic reactions, but almost any food has the potential to trigger an allergy.

Foods most likely to cause anaphylaxis are peanuts, tree nuts and shellfish.

Keep in mind that, if you are allergic to a specific food, you might be allergic to related foods. For example, a person allergic to walnuts may also be allergic to pecans and persons allergic to shrimp may not tolerate crab and lobster. Likewise, a person allergic to peanuts may not tolerate one or two other members of the legume family, such as soy, peas or certain beans. Clinical research of individuals with food allergy, however, has demonstrated that the overwhelming majority of patients with food allergy are only allergic to one or two diverse foods. Finish restriction of every foods in one botanical family based on an allergy to one of its members is rarely necessary.

Discuss these issues with your allergist.

Once My Allergy Is Identified, How Is It Treated?

Once the diagnosis of food allergy is confirmed, the most effective treatment is not eating the offending food in any form. Therefore, the patient must be vigilant in checking ingredient labels of food products and learning other names of identification of the responsible food or food additive to make certain it is not present. When you eat in a restaurant, you must be particularly vigilant and you should take emergency medicines with you if you own a history of severe reactions.

Waiters (and sometimes the kitchen chef) are not always aware of the exact ingredients of each item on the restaurant’s menu.

All patients with food allergies must make some changes in the foods they eat. Special food-allergy cookbooks, patient support groups and registered dietitians can provide valuable assistance regarding your diet. Your allergist can direct you to these resources.

Food Allergy Challenge Testing

Foods can cause numerous diverse types of allergic symptoms. Some persons experience gastrointestinal problems such as cramping, constipation or diarrhea.

Other persons suffer from skin rashes (hives or eczema). Less commonly, some may experience serious life-threatening reactions such as: asthma, throat closing or loss of consciousness. A food that causes allergic symptoms generally causes similar symptoms on each repeated exposure, provided that the same quantity of food is eaten each time (rarely symptoms can be more severe). Some persons are allergic only to raw foods while others are allergic only to cooked foods. (Most persons will react to both). Extremely little amounts of foods may trigger allergic reactions and as a result, are often hard to identify.

Food allergy symptoms can be immediate; generally beginning within 2 hrs. of ingestion, or delayed; in which symptoms which may not develop for up to 72 hrs. «Immediate» food allergies are suspected when allergic antibodies (IgE) are detected in the blood by laboratory RAST testing or by skin prick testing. The presence of allergic antibodies to foods alone is generally not sufficient to diagnose a food allergy. The confirmation of food allergy often requires challenge testing. Challenge testing is performed only in situations in which a food is suspected of causing non-life threatening symptoms.

If a food were strongly suspected of causing dizziness, throat swelling, (body tissue swelling) or shortness of breath, then challenge testing would not generally be recommended.

RAST testing reports the presence of allergic antibodies in the blood. Typically they are given numerical scores/classes (0 to 6). Class 0-1 is called «equivocal» and is rarely if ever significant. The higher the RAST class/score, the more likely it is that a true food allergy exists. Challenge testing should start with the highest-RAST class foods and continue until all positive foods own been tested.

Allergy symptoms that repeatedly develop after challenge testing with a food confirms sensitivity (allergy) and the lack of allergic symptoms generally disproves allergy. Not every RAST or skin test positive foods will cause allergy symptoms. Foods that are RAST or skin test negative rarely if ever cause immediate allergy symptoms. To be absolutely certain no allergy exists, challenge testing is occasionally recommended when skin testing and/or RAST testing is negative. (Challenge testing to RAST or skin test negative foods is generally not necessary).

Childhood eczema is the most common disease in which challenge testing is used to confirm food allergy.

If eczema is the only allergic symptom thought to be triggered by foods, it is generally extremely safe to act out food challenge testing and this can be done at home. Challenge testing is often recommended when multiple foods are noted to own stimulated allergic antibodies to determine which of the foods are most likely to be causing the allergic symptoms. If serious allergic symptoms are possibly due to a food (but unlikely) (i.e. no allergic antibodies can be detected), challenge testing may occasionally be recommended, but this should be done only in a safer environment such as a hospital ER waiting room.

Again it must be stressed that if testing has detected allergic antibodies to a food and serious allergic symptoms are likely to own occurred following ingestion, avoidance is the only safe recommendation.

Before challenge testing is done, every suspected foods are generally eliminated from the diet for at least 2 weeks (or at least those foods with a RAST class 2 or greater score).

Selecting only RAST test negative foods to eat is the «best» way to develop an elimination diet. Anti-histamine use should be stopped at least 5 days before challenge testing. Food challenges are done with only one food at a time. The food should be eaten slowly over a one hour time period and only water should be used as a drink. The largest quantity of the food that is ever generally eaten should be consumed (i.e. a normal portion). No other foods should be given for 3 hours and no additional foods suspected of causing allergy (RAST positive foods) should be eaten for at least two days to observe for the development of any «delayed» allergic symptoms.

If allergic symptoms develop at any time during the challenge test, the allergy medications contained in the key chain carrier that we own provided to you should be taken. The Epi-pen is used for severe life-threatening symptoms such as throat closing, severe cough (possible asthma), wheezing, shortness of breath or dizziness/passing out. If an Epi-pen is ever used you should call 911 immediately after.

If allergic symptoms are thought to happen following a challenge test, repeating this challenge on another day may be necessary to be certain it has caused the problem. In children, finish avoidance of any food proved to be causing allergic symptoms should continue for at least 2 years before re-exposure is attempted.

Peanut, tree nuts, egg and seafood allergies are less likely to be ever «out-grown.» Food allergies in adults do not typically ever «go away.» If you do not understand challenge testing after reading this instruction sheet please call 499-0033 for further clarification before beginning. Never act out a challenge test on any food suspected of causing allergic reactions without a doctor’s approval.

Drs. Michael & Adrianne Vaughn

Food Allergy

While an estimated 40 to 50 million Americans own allergies,

only 1 percent to 2 percent of every adults are allergic to foods or food additives.

Eight percent of children under age 6 own adverse reactions to ingested foods;

only 2 percent to 5 percent own confirmed food allergies.

The following

information addresses commonly asked questions regarding food allergy.

What Are Symptoms of Food Allergy?

Allergic reactions to foods typically start within minutes to a few hours after eating the offending food. The frequency and severity of symptoms vary widely from one person to another. Mildly allergic persons may only suffer a runny nose with sneezing, while highly allergic persons may experience severe and life-threatening reactions, such as asthma or swelling of the tongue, lips or throat.

The most common symptoms of food allergy involve the skin and intestines.

Skin rashes include hives and eczema. Intestinal symptoms typically include vomiting, nausea, stomach cramps, indigestion and diarrhea. Other symptoms can be asthma, with cough or wheezing; rhinitis, often including itchy, stuffy, runny nose and sneezing; and rarely, anaphylaxis, a severe allergic reaction that may be life threatening.
Because these symptoms can be caused by a number of diverse diseases other than food allergy, your allergist-immunologist may desire to examine you to law them out as the source of your problem.

What if I Accidentally Eat a Food I’m Allergic to?

Individuals with food allergy should own a clearly defined plan of action for handling situations in which they accidentally ingest a food allergen.

Own a list of symptoms and your doctor’s instructions for treatment posted in a prominent put in your kitchen. Oral antihistamines can be extremely useful in treating numerous of the early symptoms of a mild allergic reaction to a food.

Persons with histories of severe reactions need to be instructed in when and how to give themselves a shot of epinephrine (adrenaline) in the event of a severe allergic reaction. This medication is available in easy-to-use injectable devices and should be carried by persons with histories of severe allergic reactions. You should be taken to the hospital or call 911 and arrange for follow-up medical care for a severe reaction.

Bracelets or necklaces may be worn to quickly alert medical personnel or other caretakers about food allergies.

Will I Ever Be Capable To Eat These Foods Again?

In some cases, particularly in children, strict adherence to an elimination diet appears to promote the process of outgrowing a food allergy. For example, the vast majority of patients with documented allergic reactions to eggs, cows milk and soy eventually become tolerant to these foods. Allergies to peanuts, tree nuts, fish and shellfish, however, typically final a lifetime and are not outgrown. Overall, approximately one-third of children and adults will eventually be free of their allergic reactions to foods after rigorously following appropriate diets free of the offending food allergens.

After you own eliminated foods responsible for allergic reactions for a period of at least six months, your allergist may recommend that you undergo an oral food challenge under observation to reassess your symptoms.

If you own no reaction and can ingest a normally prepared portion of the food, you will be capable to safely reintroduce this food into your diet. If any symptoms of an allergic reaction do happen, the dietary restriction will need to be continued.

If you own had a severe immediate-type allergic reaction to a certain food, such as an anaphylactic reaction to peanuts, your allergist-immunologist may recommend that you never again eat this food and rarely would a food challenge be needed to confirm the history.

Remember, in some extremely allergic persons a extremely little quantity of an allergenic food can produce a life-threatening reaction.

Patients who use caution and carefully follow an allergist’s advice can bring food allergy under control. Please contact your allergist-immunologist with further questions and concerns about food allergy.

Download theFood Allergy Action Planand theSchool Medication Formif you need an updated one.

© Copyright 2000 American College of Allergy, Asthma and Immunology

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

See also: Patch test (finite elements)

A patch test is a method used to determine whether a specific substance causes allergicinflammation of a patient’s skin. Any individual suspected of having allergic contact dermatitis or atopic dermatitis needs patch testing.

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 little 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, perfume, toiletries, hair dyes, medicine, pharmaceutical items, food, drink, preservative, and other additives.


Interpretation of results

The dermatologist or allergist will finish a record form at the second and third appointments (usually 48 and 72/96 hour readings). The result for each test site is recorded. One system used is as follows:

  1. Weak positive (+)
  2. Equivocal / uncertain (+/-)
  3. Negative (-)
  4. Strong positive (++)
  5. Irritant reaction (IR)
  6. Extreme reaction (+++)

Irritant reactions include miliaria (sweat rash), follicular pustules, and burn-like reactions. Uncertain reactions refer to a pink area under the test chamber.

Feeble positives are slightly elevated pink or red plaques, generally with mild vesiculation. Strong positives are ‘papulovesicles’ and extreme reactions own spreading redness, severe itching, and blisters or ulcers.

Relevance is sure by exposure to the positive allergen(s), and is rated as definite, probable, possible, past, or unknown. For an allergen to own definite relevance, the product the patient is exposed to must be tested and also be positive in addition to the test allergen. Probable would be used to describe a positive allergen ingredient which is in a product the patient uses (i.e., quaternium-15 listed in a moisturizing cream used on the sites of dermatitis).

Interpretation of the results requires considerable experience and training. A positive patch test might not explain the present skin problem, since the test only indicates that the individual became allergic during encounters with that chemical at some point in their life. Relevance, therefore, has to be established by determining the causal relationship between the positive test and the eczema. The confirmation of relevance will happen after the patient has avoided exposure to the chemical and after he has noticed that the improvement or clearance of his dermatitis is directly related to this avoidance.

This outcome generally occurs within four to six weeks after stopping the exposure to the chemical.

If every patch tests are negative, the allergic reaction is probably not due to an allergic reaction to a contactant. It is possible, however, that the patient was not tested for other chemicals that can produce allergic reactions on rare occasions. If the suspicion is high in spite of negative patch testing, further investigation might be required.


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