Aeroallergen
Encyclopedia
An Aeroallergen is any airborne substance, such as pollen
or spore
s, which triggers an allergic reaction.
", because it is most prevalent during hay
ing season, from late May to the end of June in the Northern Hemisphere; but it is possible to suffer from hay fever throughout the year.
The pollen which causes hay fever varies from person to person and from region to region; generally speaking, the tiny, hardly visible pollens of wind-pollinated
plant
s are the predominant cause. Pollens of insect-pollinated
plants are too large to remain airborne and pose no risk.
Examples of plant pollen commonly responsible for hay fever include:
The time of year at which hay fever symptoms manifest themselves varies greatly depending on the types of pollen to which an allergic reaction is produced. The pollen count, in general, is highest from mid-spring to early summer. As most pollens are produced at fixed periods in the year, a long-term hay fever sufferer may also be able to anticipate when the symptoms are most likely to begin and end, although this may be complicated by an allergy to dust particles.
s, for spore ejection. These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolyte
s in the fluids of the ascus that lead to explosive discharge of the ascospores into the air. The forcible discharge of single spores termed ballistospores involves formation of a small drop of water (Buller's drop), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g
. Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs.
and other allergic foodstuffs may become airborne, thus triggering allergic reactions in susceptible individuals, especially children.
However, one report notes:
infiltration of gastrointestinal (GI) tissue, first described by Kaijser in 1937
. Aeroallergens can cause EG.
The stomach
is the organ
most commonly affected, followed by the small intestine
and the colon
.
As a part of host defense
mechanism, eosinophil is normally present in gastrointestinal mucosa, though finding in deeper tissue
is almost always pathologic
. What triggers such dense infiltration in EG is not clear. It is possible that different pathogenetic
mechanisms of disease is involved in several subgroups of patients. Food allergy
and variable IgE
response to food substances has been observed in some patients which implies role of hypersensitive
response in pathogenesis. Many patients indeed have history of other atopic
conditions like eczema
, asthma
etc.
Eosinophil recruitment into inflammatory tissue is a complex process, regulated by a number of inflammatory
cytokines. In EG cytokines IL-3
, IL-5
and granulocyte macrophage colony stimulating factor (GM-CSF) may be behind the recruitement and activation. They have been observed immunohistochemically
in diseased intestinal wall
.
In addition eotaxin
has been shown to have an integral role in regulating the homing
of eosinophils into the lamina propria
of stomach and small intestine
.
In the allergic subtype of disease, it is thought that food allergens cross the intestinal mucosa and trigger an inflammatory response that includes mast cell
degranulation and recruitment of eosinophils.
EG is "managed" (treated) with corticosteroid
s, with a 90% response rate in some studies. Various steroid sparing agents e.g. sodium cromoglycate (a stabilizer of mast cell membranes
), ketotifen
(an antihistamine
), and montelukast
(a selective, competitive leukotriene receptor antagonist
) have been proposed, centering around an allergic hypothesis, with mixed results. An elimination diet may be successful if a limited number of food allergies are identified.
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
or spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s, which triggers an allergic reaction.
Pollens
Aeroallergens include the pollens of specific seasonal plants is commonly known as "hay feverHay Fever
Hay Fever is a comic play written by Noël Coward in 1924 and first produced in 1925 with Marie Tempest as the first Judith Bliss. Laura Hope Crews played the role in New York...
", because it is most prevalent during hay
Hay
Hay is grass, legumes or other herbaceous plants that have been cut, dried, and stored for use as animal fodder, particularly for grazing livestock such as cattle, horses, goats, and sheep. Hay is also fed to pets such as rabbits and guinea pigs...
ing season, from late May to the end of June in the Northern Hemisphere; but it is possible to suffer from hay fever throughout the year.
The pollen which causes hay fever varies from person to person and from region to region; generally speaking, the tiny, hardly visible pollens of wind-pollinated
Anemophily
Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms or angiosperms ....
plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s are the predominant cause. Pollens of insect-pollinated
Entomophily
Entomophily is a form of pollination whereby pollen is distributed by insects. Several insect are reported to be responsible for the pollination of many plant species, particularly bees, Lepidoptera , wasps, flies, ants and beetles. Some plant species co-evolved with a particular pollinator, such...
plants are too large to remain airborne and pose no risk.
Examples of plant pollen commonly responsible for hay fever include:
- Trees: such as birch (Betula), alder (Alnus), cedar (Cedrus), hazel (Corylus), hornbeam (Carpinus), horse chestnut (AesculusAesculusThe genus Aesculus comprises 13-19 species of woody trees and shrubs native to the temperate northern hemisphere, with 6 species native to North America and 7-13 species native to Eurasia; there are also several hybrids. Species are deciduous or evergreen...
), willow (Salix), poplarPoplarPopulus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....
(Populus), plane (PlatanusPlatanusPlatanus is a small genus of trees native to the Northern Hemisphere. They are the sole living members of the family Platanaceae....
), linden/lime (TiliaTiliaTilia is a genus of about 30 species of trees native throughout most of the temperate Northern Hemisphere. The greatest species diversity is found in Asia, and the genus also occurs in Europe and eastern North America, but not western North America...
) and olive (OleaOleaOlea is a genus of about 40 species in the family Oleaceae, native to warm temperate and tropical regions of southern Europe, Africa, southern Asia and Australasia. They are evergreen trees and shrubs, with small, opposite, entire leaves...
). In northern latitudes birch is considered to be the most important allergenic tree pollen, with an estimated 15–20% of hay fever sufferers sensitive to birch pollen grains. Olive pollen is most predominant in Mediterranean regions. - Grasses (Family PoaceaePoaceaeThe Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...
): especially ryegrassRyegrassRyegrass is a genus of nine species of tufted grasses in the Pooideae subfamily of the Poaceae family. Also called tares , these plants are native to Europe, Asia and northern Africa, but are...
(Lolium sp.) and timothyTimothy-grassTimothy-grass , is an abundant perennial grass native to most of Europe except for the Mediterranean region. It grows to 50–150 cm tall, with leaves up to 45 cm long and 1 cm broad. The flowerhead is 7–15 cm long and 8–10 mm broad, with densely packed spikelets...
(Phleum pratense). An estimated 90% of hay fever sufferers are allergic to grass pollen. - Weeds: ragweedRagweedRagweeds are flowering plants in the genus Ambrosia in the sunflower family Asteraceae. Common names include bitterweeds and bloodweeds....
(Ambrosia), plantain (PlantagoPlantagoPlantago is a genus of about 200 species of small, inconspicuous plants commonly called plantains. They share this name with the very dissimilar plantain, a kind of banana. Most are herbaceous plants, though a few are subshrubs growing to 60 cm tall. The leaves are sessile, but have a narrow...
), nettleNettleNettles constitute between 24 and 39 species of flowering plants of the genus Urtica in the family Urticaceae, with a cosmopolitan though mainly temperate distribution. They are mostly herbaceous perennial plants, but some are annual and a few are shrubby...
/parietaria (UrticaceaeUrticaceaeUrticaceae, or the nettle family, is a family of flowering plants. The family name comes from the genus Urtica . Urticaceae includes a number of well-known and useful plants, including the aforementioned nettles, Ramie , māmaki , and ajlai .The family includes approximately 2600 species, grouped...
), mugwort (Artemisia), Fat henFat HenFat hen or fat-hen may refer to:* Hen and chicks, common name for a group of small succulent flowering plants native to Europe and northern Africa* Fat Hen, common name for Aristolochia rotunda , a perennial herb native to Southern Europe...
(ChenopodiumChenopodiumChenopodium is a genus of about 150 species of perennial or annual herbaceous flowering plants known as the goosefoots, which occur almost anywhere in the world. It is placed in the family Amaranthaceae in the APG II system; older classifications separate it and its relatives as Chenopodiaceae, but...
) and sorrelSorrelCommon sorrel or garden sorrel , often simply called sorrel, is a perennial herb that is cultivated as a garden herb or leaf vegetable...
/dock (RumexRumexThe docks and sorrels, genus Rumex L., are a genus of about 200 species of annual, biennial and perennial herbs in the buckwheat family Polygonaceae....
)
The time of year at which hay fever symptoms manifest themselves varies greatly depending on the types of pollen to which an allergic reaction is produced. The pollen count, in general, is highest from mid-spring to early summer. As most pollens are produced at fixed periods in the year, a long-term hay fever sufferer may also be able to anticipate when the symptoms are most likely to begin and end, although this may be complicated by an allergy to dust particles.
Spores
In fungi, both asexual and sexual spores or sporangiospores of many fungal species are actively dispersed by forcible ejection from their reproductive structures, which travel through the air over long distances. Many fungi thereby possess specialized mechanical and physiological mechanisms as well as spore-surface structures, such as hydrophobinHydrophobin
Hydrophobins are a class of small, cysteine rich proteins that are expressed only by filamentous fungi. They are known for their capability of forming a hydrophobic coating on a surface of an object. They were first discovered and separated in Schizophyllum commune in 1991...
s, for spore ejection. These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolyte
Osmolyte
Osmolytes are compounds affecting osmosis. They are soluble in the solution within a cell, or in the surrounding fluid, e.g. as plasma osmolytes. They play a role in maintaining cell volume and fluid balance. For example, when a cell swells due to external osmotic pressure, membrane channels open...
s in the fluids of the ascus that lead to explosive discharge of the ascospores into the air. The forcible discharge of single spores termed ballistospores involves formation of a small drop of water (Buller's drop), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g
G-force
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
. Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs.
Foodstuffs
It is thought that peanutsPeanuts
Peanuts is a syndicated daily and Sunday American comic strip written and illustrated by Charles M. Schulz, which ran from October 2, 1950, to February 13, 2000, continuing in reruns afterward...
and other allergic foodstuffs may become airborne, thus triggering allergic reactions in susceptible individuals, especially children.
However, one report notes:
Eosinophilic gastroenteritis
Eosinophilic gastroenteritis (EG) is a rare and heterogeneous condition characterized by patchy or diffuse eosinophilicEosinophilic
Eosinophilic refers to the staining of certain tissues, cells, or organelles after they have been washed with eosin, a dye.Eosin is an acidic dye; thus, the structure being stained is basic....
infiltration of gastrointestinal (GI) tissue, first described by Kaijser in 1937
. Aeroallergens can cause EG.
The stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
is the organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
most commonly affected, followed by the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
and the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
.
As a part of host defense
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
mechanism, eosinophil is normally present in gastrointestinal mucosa, though finding in deeper tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
is almost always pathologic
Pathology (disambiguation)
Pathology and -logia, study of) is a medical field specializing in the categorization of diseases. Pathological is the adjective form of the term.Pathology may also refer to:- In science :...
. What triggers such dense infiltration in EG is not clear. It is possible that different pathogenetic
Pathogenesis
The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
mechanisms of disease is involved in several subgroups of patients. Food allergy
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
and variable IgE
IGE
IGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...
response to food substances has been observed in some patients which implies role of hypersensitive
Hypersensitivity
Hypersensitivity refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. These reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized state of the host. The four-group classification...
response in pathogenesis. Many patients indeed have history of other atopic
Atopy
Atopy or atopic syndrome is a predisposition toward developing certain allergic hypersensitivity reactions.Atopy may have a hereditary component, although contact with the allergen must occur before the hypersensitivity reaction can develop ....
conditions like eczema
Eczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
, asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
etc.
Eosinophil recruitment into inflammatory tissue is a complex process, regulated by a number of inflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
cytokines. In EG cytokines IL-3
IL-3
IL-3 may refer to:* Interleukin 3* Illinois' 3rd congressional district* Illinois Route 3...
, IL-5
IL-5
IL 5 or IL-5 may refer to:* Interleukin 5* Illinois' 5th congressional district* Illinois Route 5...
and granulocyte macrophage colony stimulating factor (GM-CSF) may be behind the recruitement and activation. They have been observed immunohistochemically
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
in diseased intestinal wall
.
In addition eotaxin
Eotaxin
Eotaxin may refer to:* CCL11 * CCL24 * CCL26...
has been shown to have an integral role in regulating the homing
Homing
Homing is the process of determining the location of something, sometimes the source of a transmission, and going to it.More specifically, it may refer to:*Infrared homing*Semi-active radar homing*Active radar homing*Acoustic homing*Homing...
of eosinophils into the lamina propria
Lamina propria
The lamina propria is a constituent of the moist linings known as mucous membranes or mucosa, which line various tubes in the body ....
of stomach and small intestine
.
In the allergic subtype of disease, it is thought that food allergens cross the intestinal mucosa and trigger an inflammatory response that includes mast cell
Mast cell
A mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...
degranulation and recruitment of eosinophils.
EG is "managed" (treated) with corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s, with a 90% response rate in some studies. Various steroid sparing agents e.g. sodium cromoglycate (a stabilizer of mast cell membranes
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
), ketotifen
Ketotifen
Ketotifen is a second-generation H1-antihistamine and mast cell stabilizer. It is most commonly sold in as a salt of Fumaric Acid, Ketotifen fumarate, and is available in two forms. In its ophthalmic form, it is used to treat allergic conjunctivitis, or the itchy red eyes caused by allergies. In...
(an antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...
), and montelukast
Montelukast
Montelukast is a leukotriene receptor antagonist used for the maintenance treatment of asthma and to relieve symptoms of seasonal allergies. It is usually administered orally...
(a selective, competitive leukotriene receptor antagonist
Leukotriene antagonist
A leukotriene antagonist is a drug that inhibits leukotrienes, which are fatty compounds produced by the immune system that cause inflammation in asthma and bronchitis, and constrict airways....
) have been proposed, centering around an allergic hypothesis, with mixed results. An elimination diet may be successful if a limited number of food allergies are identified.
See also
- AerobiologyAerobiologyAerobiology is a branch of biology that studies organic particles, such as bacteria, fungal spores, very small insects, pollen grains and viruses, which are passively transported by the air...