TO ENVIRONMENTAL
AIRBORNE ALLERGENS
4b
Key messages
Measuring exposure to environmental airborne allergens
in an air sample. A dust sample is collected from the bed, carpet or sofa by vacuuming a square yard area of the bed/carpet/sofa per 2 minutes with a vacuum clean- er with a collection device. The presence of allergens is quantified with an ELISA test. Recently, an alternative wipe sampling method has been implemented to collect allergens from floor dust, where allergens are measured by a re- al-time quantitative PCR meth- odology. However, methods using settled dust might not provide ac- curate measurements of inhaled allergens. To measure airborne allergens in the air, a technique has been developed that involves collecting an integrated total suspended particulate sample through an impactor. Extracts of air samples are then analyzed by a
modified ELISA using an amplifica- tion of the generated colorimetric signal.
The prevalent outdoor allergens are pollens and molds. Usually, pollen and mold counts are as- sessed,and not their derived aller- gens.
A pollen count is nothing more than a measurement of how much pollen is in the air. It is expressed in terms of a concentration of pol- len in the air in a specific area at a certain point in time. The exact measure is grains of pollen per cu- bic meter over a 24 hour period. Mold counts, like pollen counts, are a measurement of how many mold spores are in the air in a certain area at any given point in time. Monitoring pollen and mold counts on a daily basis during the
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TABLE 1
Common airborne allergens and possible reaction(s)
Allergens Where, when
Pollen Lpl p 1, Phl p5, Cyn d1, Amb a 1, Bet v ... Outdoors Spring/summer/autumn Mold Alt 1, Cla 1 ...
Both indoors (perennial) and outdoors (seasonal) .
Indoors, molds can be found in any moist, dark place. Outdoors, mold results from vegetation degradation.
Mold floats easily in the air. House Dust mite (HDM)
Dermatophagoïdespteronyssi- nus (European HDM), Dermato- phagoïdes farina (American HDM), Blomia tropiclais. Derp 1, Derf 1, Blo...
Indoor
Found in house dust, mattresses, bedding, upholstered furniture, carpets and cur- tains
HDM feed on shedded flakes of skin HDM thrive in warm and humid environ- ments.
Pets Indoor
Major allergens are proteins secreted by oil glands in the animals' skin and shedded in dander as well as saliva proteins, which sticks to the fur when the animal licks it- self. Urine is also a source of allergens. When the substance carrying the aller- gens dries they become airborne
Cat (Feld1), Dog (Can1)
Hamster, squirrel,rabbit
Indoor/occupational
Urine is the major source of allergens from these animals.
Pests
Urine is the major source of allergens from these animals.
Mouse, rat, (Mus m1, Rat 1) Cockroach Blatella germanica
(German cockroach) (Bla g 1)
Tiny protein particles shed or excreted by- cockroaches
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seasons when they are present is one of the most proactive steps to control asthma and allergies.Pol- len and mold counts are collected using a special sampling trap that is typically placed on a rooftop several stories above the ground (Figure 2). The device has a sticky surface that collects grains of pol- len and mold spore from the air. Specific pollen and mold are rec- ognized using an electronic micro- scope.
Recent data have shown that pol- len and mold counts do not repre- sent allergen exposure. Air can be sampled for pollen and mold aller- gens with a high-volume cascade impac to requipped with stages for particulate matter (PM)>10 μm, 10 μm>PM>2.5 μm, and 2.5 μm>PM>0.12 μm. Allergenis de- termined with specific ELISA. Precise assessment of allergen concentrations is needed to define the exposure thresholds inducing sensitization, symptoms and exac- erbations of allergic diseases.
KEY REFERENCES
1. Raulf-Heimsoth M, Buters J, Chap- man M, Cecchi L, de Blay F, Doekes G, et al. Monitoring of occupational and environmental aeroallergens- EAACI Position Paper. Allergy (in press)
2. Polzius R, Wuske T, Mahn J. Wipe test for the detection of indoor al- lergens. Allergy 2002;57:143-145. 3. Krop EJ, Jacobs JH, Sander I,
Raulf-Heimsoth M, Heederik DJ. Allergens and β-Glucans in Dutch Homes and Schools: Character- izing Airborne Levels. PLoS One 2014;9: e88871.
4. Buters JT, Weichenmeier I, Ochs S, Pusch G, Kreyling W, Boere AJ et al. The allergen Bet v 1 in fractions of ambient air deviates from birch pollen counts. Allergy 2010;65:850- 858.
Definition of objectives and setting Exposure assessment strategy
Sampling methods Procedure Allergen quantification
Results in view of monitoring
Figure 1 Stepwise selection process of methods and tools of allergen assessment (modified from ref. 1)
Figure 2 Pollen and mold assessment: A: pollen trap; B and E: ELISA measurement; C and D:microscopic evaluation of pollens and molds.
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• Environmental risk factors that may influence food allergy, together with atopy, include the “hygiene hypothesis”, vitamin D insufficiency, reduced consumption of healthful dietary fats and antioxidants, and obesity
• Theories suggesting early infant ingestion of food allergens as a risk for allergy have been substantially disprove
• Early infant avoidance of food allergens could be a risk factor for allergy due to bypassing oral tolerance during a period of sensitizing cutaneous exposure
• Food allergy is the result of a complex interaction of genetic, immunologic and environmental influences, indicating a challenge for identifying effective prevention strategies
The prevalence of food allergy appears to have increased. Envi- ronmental factors must account for the apparent rise, not genetic predisposition. An over-arching effect may be the immune dys- regulation attributable to the “hygiene hypothesis”. Additional theories to explain increased ato- py, with food allergy as a bystand- er, include vitamin D insufficiency attributable to greater use of sun- screens and less time outdoors, reduced consumption of healthful omega-3-polyunsaturated fatty acids and antioxidants, and in- creased obesity, which may repre- sent an inflammatory state. How- ever, for environmental influence on food allergy in particular, the role of exposure to food proteins becomes relevant.
Probably as a response to early studies suggesting that infants ex- posed to whole cow milk proteins were at higher risk of milk aller- gy compared to those receiving breast milk or hypoallergenic for- mula, among other observations, various expert panels and profes- sional organizations suggested avoidance of allergens for infants at risk. Some guidelines included allergen avoidance during preg- nancy and lactation. The goal was