Allergen

An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.

In technical terms, an allergen is an antigen that is capable of stimulating a

The United States Food and Drug Administration recognizes nine foods as major food allergens: peanuts, tree nuts, eggs, milk, shellfish, fish, wheat, soy, and most recently sesame,^[3] as well as sulfites (chemical-based, often found in flavors and colors in foods) at 10ppm and over.^{[citation needed]} In other countries, due to differences in the genetic profiles of their citizens and different levels of exposure to specific foods, the official allergen lists will vary. Canada recognizes all nine of the allergens recognized by the US as well as mustard.^[4] The European Union additionally recognizes other gluten-containing cereals as well as celery and lupin.^{[citation needed]}

Another allergen is

In addition to foreign proteins found in foreign serum (from blood transfusions) and vaccines, common allergens include:

• Animal products
  • Fel d 1 (Allergy to cats)
  • fur and dander
  • calyx
  • wool
  • dust mite
    excretion
• Drugs
  • penicillin
  • sulfonamides
  • salicylates (also found naturally in numerous fruits
    )
• Foods
  • celery and celeriac^[10]
  • corn or maize
  • eggs (typically albumen, the white)
  • fruit
    • pumpkin, egg-plant
  • legumes
    • beans
    • peas
    • peanuts
    • soybeans
  • milk
  • seafood
  • sesame
  • soy
  • tree nuts
    • pecans
    • almonds
  • wheat
• Insect stings
  • venom
  • wasp sting venom
  • mosquito bites
• Mold spores
• Top 5 allergens discovered in patch tests in 2005–06:
  • nickel sulfate
    (19.0%)
  • Balsam of Peru (11.9%)
  • fragrance
    mix I (11.5%)
  • quaternium-15 (10.3%), and
  • neomycin (10.0%).^[11]
• Metals
  • nickel
  • chromium
• Other
  • latex
  • wood
• Plant
  hay fever
  )
  • timothy-grass
  • weeds — ragweed, plantago, nettle, Artemisia vulgaris, Chenopodium album, sorrel
  • Ashe juniper
    , Alstonia scholaris

Seasonal allergy

Seasonal allergy symptoms are commonly experienced during specific parts of the year, usually during spring, summer or fall when certain trees or grasses pollinate. This depends on the kind of tree or grass. For instance, some trees such as oak, elm, and maple pollinate in the spring, while grasses such as Bermuda, timothy and orchard pollinate in the summer.

Grass allergy is generally linked to hay fever because their symptoms and causes are somehow similar to each other. Symptoms include

If both parents have had allergies in the past, there is a 66% chance for the individual to experience seasonal allergies, and the risk lowers to 60% if just one parent has had allergies.^[citation needed] The immune system also has strong influence on seasonal allergies, because it reacts differently to diverse allergens like pollen. When an allergen enters the body of an individual that is predisposed to allergies, it triggers an immune reaction and the production of antibodies. These allergen antibodies migrate to mast cells lining the nose, eyes, and lungs. When an allergen drifts into the nose more than once, mast cells release a slew of chemicals or histamines that irritate and inflame the moist membranes lining the nose and produce the symptoms of an allergic reaction: scratchy throat, itching, sneezing and watery eyes. Some symptoms that differentiate allergies from a cold include:^[14]

• No fever.
• Mucous secretions are runny and clear.
• Sneezes occurring in rapid and several sequences.
• Itchy throat, ears and nose.
• These symptoms usually last longer than 7–10 days.

Among seasonal allergies, there are some allergens that fuse together and produce a new type of allergy. For instance, grass pollen allergens cross-react with food allergy proteins in vegetables such as onion, lettuce, carrots, celery, and corn. Besides, the cousins of birch pollen allergens, like apples, grapes, peaches, celery, and apricots, produce severe itching in the ears and throat. The cypress pollen allergy brings a cross reactivity between diverse species like olive, privet, ash and Russian olive tree pollen allergens. In some rural areas, there is another form of seasonal grass allergy, combining airborne particles of pollen mixed with mold.^[15] Recent research has suggested that humans might develop allergies as a defense to fight off parasites. According to Yale University Immunologist Ruslan Medzhitov, protease allergens cleave the same sensor proteins that evolved to detect proteases produced by the parasitic worms.^[16] Additionally, a new report on seasonal allergies called "Extreme allergies and Global Warming", have found that many allergy triggers are worsening due to climate change. 16 states in the United States were named as "Allergen Hotspots" for large increases in allergenic tree pollen if global warming pollution keeps increasing. Therefore, researchers on this report claimed that global warming is bad news for millions of asthmatics in the United States whose asthma attacks are triggered by seasonal allergies.^[17] Indeed, seasonal allergies are one of the main triggers for asthma, along with colds or flu, cigarette smoke and exercise. In Canada, for example, up to 75% of asthmatics also have seasonal allergies.^[18]

Seasonal allergy diagnosis

Based on the symptoms seen on the patient, the answers given in terms of symptom evaluation and a physical exam, doctors can make a diagnosis to identify if the patient has a seasonal allergy. After performing the diagnosis, the doctor is able to tell the main cause of the allergic reaction and recommend the treatment to follow. 2 tests have to be done in order to determine the cause: a blood test and a skin test. Allergists do skin tests in one of two ways: either dropping some purified liquid of the allergen onto the skin and pricking the area with a small needle; or injecting a small amount of allergen under the skin.^[19]

Alternative tools are available to identify seasonal allergies, such as laboratory tests, imaging tests, and nasal endoscopy. In the laboratory tests, the doctor will take a nasal smear and it will be examined microscopically for factors that may indicate a cause: increased numbers of eosinophils (white blood cells), which indicates an allergic condition. If there is a high count of eosinophils, an allergic condition might be present.^[20]

Another laboratory test is the blood test for IgE (immunoglobulin production), such as the radioallergosorbent test (RAST) or the more recent enzyme allergosorbent tests (EAST), implemented to detect high levels of allergen-specific IgE in response to particular allergens. Although blood tests are less accurate than the skin tests, they can be performed on patients unable to undergo skin testing. Imaging tests can be useful to detect sinusitis in people who have chronic rhinitis, and they can work when other test results are ambiguous. There is also nasal endoscopy, wherein a tube is inserted through the nose with a small camera to view the passageways and examine any irregularities in the nose structure. Endoscopy can be used for some cases of chronic or unresponsive seasonal rhinitis.^[21]

Fungal allergens

In 1952

Allergen immunotherapy treatment involves administering doses of allergens to accustom the body to induce specific long-term tolerance.^[44] Allergy immunotherapy can be administered orally (as sublingual tablets or sublingual drops), or by injections under the skin (subcutaneous).^[45][46] Immunotherapy contains a small amount of the substance that triggers the allergic reactions.^[47]

See also

• Asthma
• Asthmagen
• Bioaerosol
• Eczema
• Eggshell skull
• Hypoallergenic
• Immunodiagnostics
• List of allergies
• Nose filter
• Oral allergy syndrome
• Toxin

References