Archive for the ‘Allergy Testing’ Category
Monday, October 3rd, 2011
A recent venom allergy guideline¹ published by the British Society for Allergy and Clinical Immunology (BSACI) this year, makes interesting reading. They report a lifetime-risk between 60 and 90% for the UK population of being stung by a wasp (Vespid) or bee (Apis). Of those stung, up to 26% will report large painful local reactions, but significant allergic reactions only occur in about 7% of those stung (bee-keepers being a very high-risk group with severe reactions reported in 30% of those stung). Although wasp venom allergy is more common in the UK, bee-stings carry a higher risk for anaphylaxis. Any patient with a severe reaction to an insect sting should be tested for both bee and wasp venoms sensitivity, as dual-positive IgE antibodies to both insects occurs in 30%, even though they may report being clinically sensitive to only one insect. Venom desensitisation immunotherapy (VIT) or “allergy shots” are highly effective in those severely sensitive to insect stings, resulting in a cure for 95% of wasp and 80% of bee venom allery sufferers treated over the 3 year programme. Older people are more likely to develop life-threatening anaphylaxis and fatal allergic reactions (at an average age of 50 years). Children are less prone to have life-threatening allergic reactions to insects, and 80% of children with a mild venom allergy with tolerate further stings and outgrow their allergy. Once sensitised, reactions are likely to be the same in 45% stings, milder in 43% and more severe in only 12%. Fatal reactions after insect stings are rare (47 deaths in UK over a 10 year period from 1992-2001)
¹Reference: Krishna MT, Ewan PW, Diwakar L, Durham S, Frew AJ, Leech SC and Nasser SM. Diagnosis and management of hymenoptera venom allergy: British Society for Allergy and Clinical Immunology (BSACI) guidelines. Clinical and Experimental Allergy 2011:41; 1201-1220
Tags: anaphylaxis, bee sting, bsaci, hymenoptera, IgE, insect allergies, vespid, vit, wasp sting
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Monday, January 3rd, 2011
Many surgical procedures involve implanting artificial metallic components such as joint replacements (arthroplasties), plates, screws and internal “plumbing” that contain metals such as titanium, nickel, cobalt and other heavy metal alloys. Ever since mercury dental amalgam was thought to be a health hazard in the 1970’s, people have become very aware of possible side effects of foreign metallic implants. Although implants are now commonly used, there seems to be no convincing evidence that they cause local or systemic allergic or immunological problems. Some clinics offer blood tests and skin patch tests for possible heavy metal toxicities, but it must be pointed out that these tests are not scientifically validated and offer no proven diagnostic aid. They increase anxiety and lead to many people declining quality of life improving procedures such as a hip or knee repalcements for crippling arthritis, or worse still, the unnecessary removal of such prosthesis.
Reference: American Academy for Allergy and Clinical Immunology (AAAAI) website: http://www.aaaai.org/professionals/ask-the-expert/view.asp?id=9944
Tags: arthroplasty allergy, heavy metal, hip replacement allergy, metal implants, nickel allergy, titanium
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Monday, December 6th, 2010
Cow’s milk allergy is relatively common in babies (1:50) but rarely develops after one year of age. Symptom improvement on a cow’s milk-free diet and recurrence of symptoms with reintroduction of cow’s milk formula is the most accurate diagnostic procedure. Cows milk allergy may be underdiagnosed as it is common (but misguided) practice amongst UK GP’s and Paediatricians only to perform food allergy testing in children once they are 4 years or older.
Skin prick tests using fresh cow’s milk and RAST blood tests for cow’s milk protein IgE antibodies are the only reliable tests and have 60-90% accuracy. The whey (liquid) fraction of milk tends to cause most allergies, but the casein (curd) fraction triggers more severe and persistent allergies.The higher the milk-specific IgE level, the more likely there will be a clinically relevant milk allergy. High levels of Casein specific IgE antibodies indicate a higher risk for severe cows milk allergy and also for persistent cows milk allergy, On the other hand, IgG antibody testing for cow’s milk proteins (casein and b-lactoglobulin) is of no allergy diagnostic value and merely indicates exposure.
The clinical history and observation of the infant feeding are very helpful, and a family history of atopy increases the likelihood of a food allergy. Cow’s milk allergy can manifest with immediate urticaria and facial angioedema and respiratory, oral and laryngeal symptoms, as well as deteriorating eczema in addition to typical intestinal symptoms such as vomiting, diarrhoea, persistent reflux, food refusal and even anaphylaxis in severe cases.
Mildly milk-allergic infants often tolerate small amounts of processed dairy produce such as yoghurt and cheese as well as Goat’s milk. Infants with severe cow’s milk allergy will react to any traces of milk protein in partially hydrolysed milk formula, cooked foods and even breast milk, as well as any skin contact with milk proteins.
Tags: Allergy Testing, casein aliergy, cow milk allergy, IgE testing, IgG testing, lactoglobulin, whey allergy
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Monday, July 26th, 2010
Hen egg allergy is very common in infants with eczema and usually outgrown by age 6 with a few children retaining their egg allergy into adulthood. The egg white or albumin is more allergenic than the yolk and heat or cooking damages the allergen making it less allergenic. Some children will therefore tolerate cooked but not raw egg, whereas other more severely allergic children will react to all traces of egg. Early onset of egg allergy is associated with asthma at age 18 months. Fortunately the Measles (MMR) vaccine no longer contains any egg so is not contraindicated in egg allergic children. However the Influenza and Yellow Fever vaccines are grown on chick egg embryo’s and therefore may be a problem for egg allergic children.
A new ImmunoCAP f233 blood test can now determine whether hen’s egg allergy is likely to be severe and persists into adulthood. Once the IgE skin prick test or blood RAST testing show a positive allergy result for eggs, a further test for raised antibodies to the heat-stable egg protein Ovomucoid (Gal d 1) is very useful for determining if egg allergy will persist.
Ref: Ando H, Moverare R, Kondo Y et al Utility of ovomucoid-specific IgE concentrations in predicting symptomatic egg allergy. J Allergy and Clin Immunology 2008:122;583-8.
Tags: egg albumin, egg allergy, hen egg, IgE, MMR allergy, ovomucoid, rast testing, skin prick test
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Thursday, February 18th, 2010
Lactose Intolerance is a deficiency of the digestive enzyme B-galactosidase (Lactase) in the human intestine and a meal containing the cow‘s milk disaccharide sugar lactose (galactose bound to glucose) will induce frothy diarrhoea, flatulence and abdominal cramps. This is caused by undigested lactose passing into the colon where it is hydrolysed by bowel bacteria producing organic acids and gas including CO2, H2 and H2O. Symptoms do not include vomiting, rashes or nasal congestion as there is no immune response, it is purely undigested lactose that results in runny poop!
So if you do indeed have Lactose Intolerance, a proper cow’s milk challenge must theoretically give you rapid onset diarrhoea. No diarrhoea equates to no Lactose Intolerance. If your nose blocks up or they get a rash on your tummy then you probably have some additional problem other than purely lactose intolerance.
Almost all people are born with sufficient lactase but with increasing age, levels drop. Most lactose intolerant individuals tolerate small amounts of lactose in the diet and usually a full glass of fresh milk is necessary to trigger symptoms. Temporary lactose intolerance may follow a bout of viral gastroenteritis due to inflammation and hence it is best to avoid cow’s milk during the recovery period.
Lactose Intolerance may be an inherited trait affecting 10% of Caucasians and up to 80% of ethnic Africans, Asians and people of Mediterranean origin. Treatment is basically lactose avoidance or supplementation with an oral Lactase enzyme preparation such as Colief. Yoghurt is often tolerated as it contains live B-galactosidase producing bacteria.
Useful tests for diagnosing Lactose Intolerance include the popular Hydrogen Breath Test (although less reliable due to false positive results from other dietary sugar intake), as well as measuring serial blood glucose levels after a lactose containing meal, or measuring Faecal Reducing Substances (Sugars) in the watery frothy diarrhoeal stool produced as a consequence of a lactose containing meal.
References:
Joneja JMV. Food Allergy & Intolerances. Mechanisms and Management. J.A.Hall publications 2003.
Metcalfe D, Sampson H, Simon R. Food Allergy: adverse reactions to food and food additives 4th Ed. Blackwell Science 2008
Tags: colief, cows milk intolerance, diarrhoea, faecal reducing substances, flatulence, galactosidase, hydrogen breath test, lactase
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Thursday, January 14th, 2010
Irritable bowel syndrome otherwise called IBS is a common medical condition affecting the lower bowel in 1 in 5 young adults. Females are especially prone to IBS which presents with one or more of 3 cardinal symptoms:
A. Abdominal pain and spasm which eases when emptying the bowels.
B. Bloating, fullness on eating and abdominal distension with wind.
C. Change in bowel habit with passage of frequent loose mucus-laden stools (an enhanced gastro colic reflex), often alternating with episodes of constipation.
Other more serious bowel conditions such as food allergies, inflammatory colitis, stomach ulcers, intestinal infection and coeliac disease may cause similar but more intense symptoms, and will need to be excluded by testing. A few simple blood tests undertaken by your GP (such as ESR, CRP, FBC) will exclude colitis or gut infection, while specific IgE allergy testing will identify food allergy and coeliac screening measuring Tissue Transglutaminase antibodies will exclude gluten intolerance. Certain non-specific food intolerances may be triggers for IBS and these include excess fruit intake, wheat, dairy produce, onions, excess tea, coffee, alcohol and highly insoluble dietary fibre such as bran, all of which may exacerbate IBS symptoms. The artificial sweetener Sorbitol and processed starch in ready meals may also promote IBS. While emotional stress, masked depression and missed or erratic meals may also be triggers, whereas taking a regular Probiotic supplement (Acidophilus GG) and drinking plenty of filtered water every day may calm the symptoms.
Discuss any concerns you might have regarding food allergies, intolerance or colitis with your GP, Practice Nurse or a qualified Dietician.
http://www.nice.org.uk/guidance/index.jsp?action=byID&o=11927
Tags: Allergy Testing, artificial sweetener, diet and stress, Food Allergy, Food Intolerances, gluten intolerance, high fibre diet, infections, probiotics, ready meals
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Friday, December 4th, 2009
Even if allergic to the same food, not all people react to the same protein in the food. There a number of potential allergy provoking proteins found in each food.
Cow’s milk allergy sufferers may react to one of five different casein or whey proteins in milk. Hence most casein allergic children react to cheese and goats milk while whey allergic children seem to tolerate these products. Heating of milk lowers the allergy potential of the whey components. This explains why whey allergic children seem to tolerate boiled or UHT long-life cow’s milk.
The five principal allergenic proteins in cow’s milk have now been identified as Bos d 4 (alpha-lactalbumin) and Bos d 5 (beta-lactglobulin) in whey, as well as Bos d 6 (Bovine serum albumin), Bos d 8 (Casein) and Bos d lactoferrin (Bovine lactoferrin)
While in Hens’ egg white, there are four different allergenic proteins. These are Gal d 1 (Ovomucoid), Gal d 2 (Ovalbumin), Gal d 3 (Conalbumin) and Gal d 4 (Lysozyme). One of these could set off an egg allergic reaction in a sensitised individual.
In Peanut we find 9 different Ara h allergens and in Latex there are 13 different Hev b allergens, all capable of triggering a peanut or latex allergic reaction. The Latex Hev b 8 allergen, also called a Profilin is similar to the allergy provoking Profilin found in apple, banana and many other fruits.
This may seem very complicated, but a new range of allergy tests for these specific components are now available. The tests are called recombinant allergen components and confirm to which protein in a food the individual will react. Certain allergy provoking proteins such as Profilin, PR-10 proteins, Tropomyosin and Lipid Transfer Protein (LTP) can occur in unrelated food such as Hazelnut and Apple or Latex and Avocado. For example an unsuspecting Latex allergy sufferer may have an acute allergic reaction when eating Avocado, Banana, Kiwi or Chestnut for the first time.
Once the specific allergen is identified on allergy testing, the person can be advised which other foods may cause an adverse allergic reaction
Ref: Steinman H, Native & recombinant allergen components. Phadia AB 2008, ISBN 91-970475-6-2
Tags: allergen testing, cow milk allergy, egg allergy, lactglobulin, latex, lipid transfer protein, peanut allergy, profilin, recombinant allergens
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Wednesday, November 18th, 2009
A scientific study due to be published in the American medical journal Pediatics (December 2009) has found a massive 18% increase in reported food allergies amongst US children (under 18 yrs of age). This increased reporting of food allergies took place over the last decade between 1997 and 2007. While between 1993 and 2006 ambulatory visits to the doctor for food allergies have tripled. In 2007 alone, 3.9% of US children reported food allergic conditions. The most severely affected were ethnic minorities such as Hispanics. In 2005 to 2006, an estimated 9% of US children had detectable peanut IgE in their blood on allergy testing while over the same period hospitalisations with a diagnosis of food allergy also tripled. It is uncertain whether this trend is due to a true increase in food allergic diseases or represents increasing allergy testing and physician and parental food allergy awareness.
http://pediatrics.aappublications.org/cgi/content/abstract/peds.2009-1210v1
Tags: allergy in children, Allergy Testing, food allergies, Food Allergy, IgE, peanut allergy
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Thursday, November 12th, 2009
A recent study on children attending day care or nurseries by de Jongste in the American Thoracic Society journal cast some doubt on the so-called Hygiene Hypothesis for allergy development. The Hygiene Hypothesis notion that farm animal faeces exposure and childhood infections will prevent allergies has been promoted for decades. The hygiene hypothesis essentially links a more clean and sterile home environment with the overall rise in allergies seen in many developed Western counties. Poor living conditions with early exposure to germs, infections and parasites seem to shift the infant’s immune system into survival mode (TH1) and away from allergy mode (TH2) when allergy testing. However this immune switching probably occurs very early in the first few months of life. Therefore as mentioned in the American study, day care centre exposure and subsequent childhood infections may have little impact on allergy development. Particularly if the child attends a day-centre after one year of age when their immune type reactivity is more established. It still seems likely that a germ-filled household with difficult living conditions and plenty of sickly older siblings will be more protective from allergies while a sterile, insular environment in early infancy seems to promote allergies.
http://news.bbc.co.uk/2/hi/health/8241774.stm
Tags: allergy protection, Allergy Testing, children's allergies, day care allergies, hygiene hypothesis, immune switching, infections, parasite
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Thursday, October 29th, 2009
In the UK, blood tests for immunoglobulin G4 (IgG4) against foods are actively promoted for the diagnosis of food intolerance and hypersensitivity. Mounting clinical research indicates that food-specific IgG4 allergy testing does not indicate (imminent) food allergy or intolerance, but is rather a normal physiological response by the immune system after food exposure. In fact IgG4 is more likely to indicate food tolerance and that the person can safely eat that food with no adverse effect. This should not be confused with IgE which is the main allergy antibody used in allergy testing and this has an established “track record” in conventional allergy diagnosis.
Not really convinced? Have a look at these research papers:
No recommendation for IgG and IgG4 testing against foods
J. Kleine-Tebbe, I. Reese, B. K. Ballmer-Weber, K. Beyer, S. Erdmann, Th. Fuchs, M. Henzgen, A. Heratizadeh, I. Hutt egger, L. Jäger, U. Jappe, U. Lepp, B. Niggemann, et al Allergo J 2009;4: 267
Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report*
Stapel SO, Asero R, Ballmer-Weber BK, Knol EF, Strobel S, Vieths S, Kleine-Tebbe J.
Allergy 2008 July;63(7):793-796.
Unproven techniques in allergy diagnosis.
Wuthrich B.
J Investig Allergol Clin Immunol 2005;15(2):2-90
Tags: Allergy Testing, Antibody, Food Allergy, Food Intolerances, IgE, IgG
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Saturday, October 17th, 2009
The British Society for Allergy and Clinical Immunology (BSACI) has recently raised concerns about allergy testing in pharmacies.
They site a major problem being that pharmacy training involves education about medicines, not about clinical disease, patient history taking, psychology etc. This means that pharmacists do not know what the possibilities for diagnosis are in patients who present with, say, a blocked nose. (more…)
Tags: Allergy Testing, IgE, pharmacy, tests
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