Archive for the ‘Allergy Testing’ Category

Outgrowing egg allergy

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.

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High Street allergy tests mislead public

Monday, February 22nd, 2010

The Sunday Times newspaper has again produced a masterpiece of investigative journalism (Sunday 21st February 2010) highlighting the frightening number of nonsense allergy and food intolerance tests available in central London. It is amazing that there is no public watchdog to prevent these unvalidated and unscientific allergy tests from being promoted to unsuspecting members of the public by inadequately trained practitioners and nutritionalists. Well done to Gillian Passmore and the Sunday Times for again drawing attention to the issue of misleading unorthodox allergy testing.

http://www.timesonline.co.uk/tol/life_and_style/health/article7034867.ece

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Lactose Intolerance only causes diarrhoea

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

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Irritable bowel syndrome (IBS)

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

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New technologies in allergy testing

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

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18% increase in food allergies amongst US children

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

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Home hygiene, infections and allergies

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

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IgG antibody tests don’t indicate food intolerances.

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

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Should Allergy Testing be done in Pharmacies?

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…)

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