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Libro guia de alergias

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  • Allergens

  • 2

  • 3d1 House dust mite 5e1 Cat 6e5 Dog 7f1 Egg 8f2 Milk 9f3 Fish 10f4 Wheat 11f13 Peanut 12f14 Soybean 13f17 Hazelnut 14f24 Shrimp 15g6 Timothy 16i6 Cockroach 17m6 Mold 18t3 Birch 19t9 Olive 20w6 Mugwort 21w21 Wall pellitory 22 Reference Lists 23

    Contents

  • 4

  • 5d1 House dust miteDermatophagoides pteronyssinus

    Allergen descriptionDermatophagoides pteronyssinus

    Family: Pyroglyphidae

    House dust mites are one of the most common sources of sensitization in all parts of the world. Dermatophagoides pteronyssinus, D. farinae and D. microceras occur in the same areas, but the relative proportions of their distribution vary geographically. Mites have a life cycle of about 2 to 3 months. The size of the mite is up to 0.3 mm. They live in house dust and thrive in warmth and high humidity. Mites faeces seem to be the major source of allergenic exposure. They are about the size of a pollen grain and can therefore very easily become airborne and penetrate the lung alveolus (1).

    Allergen exposureDust, carpets, pillows, mattresses and upholstering furniture containing biological material, especially human dander, are reservoirs of house dust mites. Other sources of exposure are damp houses (>45% relative humidity) or dwellings at low altitudes.

    Cross-reactivityAllergens from mites have both common and species-specic determinants. Allergenic determinants are shared with other mites belonging to the Pyroglyphidae family and are highly cross-reactive with other Dermatophagoides species (2, 3). There seems to be a limited cross-reactivity with storage mites (nonpyroglyphid) (3). Some mite allergenic proteins such as tropomyosin are widely cross-reactive among invertebrates such as shrimps, snails, cockroaches and chironomids (3).

    Clinical experienceIgE-mediated reactionsStudies of house dust allergic individuals around the world have shown that house dust mites are one of the most common causes of symptoms such as perennial type asthma, rhinitis and conjunctivitis, often with nocturnal or early morning episodes (4). There is evidence that reduction of mite-allergen levels can cause a major improvement in symptoms of asthma (5). So far the only effective way to get a permanent reduction of house-dust mite allergens seems to be lowering of the air humidity and temperature together with efcient cleaning (4).

  • 6 e1 CatEpithelium and dander

    Allergen descriptionFelis domesticus

    Family: Felidae

    Allergens from cat epithelium and dander are one of the most common causes of respiratory allergic disease. Several cat allergens have been identied and characterized (1).

    Allergen exposureCarpets, mattresses and upholstered chairs are reservoirs of cat allergens. Cat allergens are carried on human clothing into environments never visited by cats. Transport of cat allergens on clothing from the domestic to the school environment is in fact a major source of cat allergens in classrooms.

    Cross-reactivityCat-allergic patients have been shown also to react to big cats e.g. ocelot, tiger and lion (2). A subgroup of cat-allergic patients also reacts to dogs and sometimes to other animals. Serum albumin is the main common component (3, 4). Extensive cross-reactivity even occurs between albumins of distantly related species such as horse, cattle, pig, rodents and furred animals (57). However, great variability exists between patients and selective sensitivity to limited numbers of species occurs. Allergy to cat dander and pork meat, also referred to as the pork/cat syndrome (8), was shown to be mediated by IgE antibodies recognizing cat and pig serum albumin (9). In addition, other kinds of meat may be a risk for patients with this type of sensitivity (10).

    Clinical experienceIgE-mediated reactionsIgE-mediated sensitization to cat is a risk factor for asthma. Allergen exposure plays a causal role in the development of bronchial hyperreactivity and of the chronic inammatory responses seen in patients with asthma (11). Infants exposed to cats developed skin prick test sensitivity about three times more often than those without such exposure (12). Furthermore, the low level cat exposure that occurs in many homes without cats can induce symptoms in some patients who are sensitive to cats (13). Tobacco smoke, prenatal and postnatal, has been shown to have an adjuvant effect on cat sensitization in exposed children (14). Allergic reactivity to pollens may also be aggravated by environmental priming with ubiquitous animal dander (15). Furthermore, allergy to cats or dogs seems to be an important risk factor for the development of laboratory animal allergy (16). Avoidance of cat allergens is an important measure to take in the treatment of sensitized asthmatics, decreasing symptoms and decreasing the need for drugs (17). Only removal of the cat leads to a lasting decrease of the allergen exposure (1820).

  • 7Allergen descriptionCanis familiaris

    Family: Canidae

    The dog, a relative of the wolf, the jackal and the fox, was one of the earliest domestic animals, living in human communities as early as 12 000 years ago. More than 800 breeds have been developed. Dog allergens have been found in serum, dander, pelt, hair and saliva (1, 2). Although allergen differences occur according to the origin of the allergen (e.g. dander or saliva), no breed-specic allergens occur. But the concentration of allergens varies within breeds and among them. Dog dander contains the highest proportion of dog-specic allergens. Animal dander is extremely lightweight and tiny in size and can stay airborne for hours.

    Allergen exposureLevels of dog allergens in houses with dogs may reach high levels. Levels in homes without dogs are generally 10 to 100 times lower, but can still be detected. In houses with dog allergens, the highest concentration appears to occur on the living-room oor, on furniture, and in bedrooms. Dog allergens can be detected also in other places, such as schools and day-care centers where dogs are not present on a regular basis. The allergens appear to be transported on clothes and may be present in relatively high concentrations.

    Cross-reactivityAn extensive cross-reactivity among the different breeds could be expected. It has been noted that many patients allergic to cats are also allergic to dogs. Many studies suggest evidence for cross-reactivity between some cat and dog allergens (35).

    Clinical experienceIgE-mediated reactionsDog dander is an important source of inhalant allergens, and may frequently induce symptoms in sensitized individuals (1, 2, 5, 6). Symptoms include asthma, allergic rhinitis and allergic conjunctivitis. 3035% of atopic individuals display allergic symptoms on exposure to dog allergens (79). Symptoms can be caused by indirect exposure to dog dander in schools, at work and on public transport. In sensitized subjects, repeated exposure to allergens also contributes to subclinical inammation, hyperresponsiveness and general worsening of asthma (10, 11). Eczema following exposure to dog allergens has been reported (12). Occupational allergy to dog may also occur in animal workers, animal pelt workers and laboratory workers.

    e5 Dog Dander

  • 8Allergen descriptionGallus spp.

    Egg is a major cause of adverse reactions in infants and hidden exposure is common. Hens eggs are composed of about 60% egg white and 30% egg yolk. Egg white contains approximately 88% water and 10% protein. The major allergens of egg white are ovomucoid, ovalbumin, ovotransferrin (also called conalbumin), and lysozyme (1).

    Allergen exposureExpected exposure Cooked or raw eggs Bread and pastry Numerous dishes like pancakes, sauces, etc.

    Unexpected exposure Candy Beverages Meat products like sausages, pts, etc.

    A great variety of foods may contain egg or traces of egg and patients allergic to egg need to be aware of egg as a frequent hidden allergen.

    Cross-reactivity Eggs from related animals Presence of shared allergens in egg-white, egg-yolk, serum and meat from hen and chicken has been demonstrated.

    f1 EggEgg white

    Clinical experienceIgE-mediated reactionsEgg-specic IgE antibodies are usually the rst antibodies to appear in children developing atopic disease. Allergy to egg is generally considered to be one of the most common causes of food allergy in infants and young children (2). When studying egg-allergic children, IgE antibodies were found in more than 65% of children with eczema and respiratory tract symptoms (3). Egg-white specic IgE antibodies may predict the development of atopic respiratory allergy. In a follow-up study of infants where the authors had concluded that egg-white sensitivity was a better indicator of atopy than total serum IgE, the infants presenting with egg-white allergy were more likely to have developed inhalant allergy by 7 years of age (4). Other studies show similar results (5, 6). Egg white is often responsible for early development of urticaria and eczema during infancy (7). Remaining egg intolerance in older children and adults may be linked to exposure to cage birds and chicken meat. Certain vaccines grown on chicken embryos have been reported to cause severe allergic reactions in patients when injected (8). Further development of vaccines seems to have decreased or even eliminated the risk for egg-allergic children (9, 10).

  • 9f2 MilkCows milk

    Allergen descriptionBos spp.

    Cows milk is a major cause of adverse reactions in infants and hidden exposure is common. There are many allergenic proteins in milk and caseins, alpha-lactalbumin and beta-lactoglobulin are considered as some of the major allergens. Caseins are heat stable allergens (1).

    Allergen exposureExpected exposure Milk, cheese an