Allergies
Allergies

Usually playing with a pet or drinking a glass of milk does not invoke a passing thought to health. However, to people with allergies, something so routine can become a significant health risk. Although, many Americans are lucky enough to be allergy-free, nearly 40% of the U.S. population may be affected by allergies. The incidence of allergies has more than doubled since the early 1970's and children seem to be especially affected by this problem. There are several theories as to why this increase has occurred, with changes in our environment due to a "western" or "post-industrialized" lifestyle playing an important role. Once these issues are clearly worked out it may be possible to apply strategies to prevent allergies.

At AIRCare we rely on means of effective treatment that involve:

  1. Making an accurate diagnosis through testing
  2. Avoidance of offending allergens when possible
  3. Use of an ever-expanding arsenal of medications and immunotherapy or allergy shots.

What is an allergy?

An allergy is present when a person's immune system attacks a substance (called an allergen) that most people's immune systems would ignore.

Classical IgE mediated allergy:

In classical allergy T-cells respond to an allergen and direct other cells to respond as well. One of these other cell types (called B-cells) produce an antibody called IgE, that then associates with Mast cells that line the respiratory tract (including nose, sinuses and lungs), skin and gastrointestinal tract. Most allergens are proteins and they trigger allergic reactions when they enter the body or come in contact with body surfaces. At this point they bind to the IgE on Mast cells triggering the release of histamine, leukotrienes and other substances that recruit inflammatory cells like the Eosinophil into sites of allergen exposure. Histamine, leukotrienes and inflammatory cells (Eosinophils) cause most of the symptoms that we associate with allergies.

Some allergens are chemicals like penicillin that alter a persons own proteins enough to trigger the immune attack or allergic reaction. Classical allergy is termed T/B cell mediated and results in high levels of IgE against the offending allergen. When we test for allergy, we are testing for IgE either by skin test or blood test. Contrary to popular belief, allergens almost never cause a reaction on the first exposure. A person must be exposed to an allergen at least once in order to make an immune response or IgE to that allergen. This is called the sensitization exposure. The next exposure then results in the allergic reaction. Once a person is sensitized or makes IgE to an allergen, reactions may increase with each subsequent exposure. However, complete avoidance of an allergen over long periods of time (years) results in diminishing levels of IgE or reactivity against the allergen, even to the point of resolution of the allergy. Unfortunately, for most allergens complete avoidance is not possible.

Non-classical allergy:

It is becoming clear that some people produce little or no IgE and seem to skip the B-cell activation stage. These people may have many of the symptoms of classical allergy but little or no IgE against the offending allergen. These people are termed T-cell mediated reactors and though they may have delayed skin reactions (occurring 6-12 hours after exposure), their immediate skin reactions and blood tests for allergens are either negative or less than impressive.

Implications for children under 5 years of age: Children develop allergies over time. Except for food allergies (due to exposure in the womb) it is rare to be born with IgE against environmental allergens. Once children are exposed to environmental allergens their T-cells begin to react. This reactivity may produce symptoms (typically chronic congestion and recurrent upper respiratory infections), but usually does not result in positive skin or blood tests for allergy. Over time B-cells are recruited and begin producing IgE. This IgE then results in positive allergy tests. This entire process can take up to 3-5 years for perennial allergens like dust mite, animal dander and mold spores, and up to 5-6 years for seasonal allergens like ragweed or grass pollen. The notion that young children can't have allergies is not true in the sense of T-cell reactivity (which can produce symptoms), but is more relevant for B-cell or IgE reactivity (which produces positive allergy tests). Thus, it becomes important to interpret the results of allergy testing in light of a child's age. Many times negative allergy tests at a young age will turn positive on re-testing one to three years later.


Types of Allergies

Environmental - most environmental allergens are airborne and cause symptoms on contact with skin or mucosal surfaces:

  • skin (eczema or allergic dermatitis)
  • nose (allergic rhinitis)
  • sinuses (rhinosinusitis, headache)
  • throat (post nasal drip, laryngitis and laryngeal edema)
  • lungs (chronic cough and asthma)
  • eyes (conjunctivitis)

Environmental allergens can be classified into outdoor or indoor and seasonal or perennial (year round) categories. Most outdoor allergens are plant pollens and are seasonal. Mold spores are the exception with measurable counts registered year round, classifying them as a perennial allergen. Mold spores do show some seasonal variation that depends largely on temperature, availability of decaying plant matter and moisture levels; with levels peaking during mid spring and late fall.

Outdoor AllergensSeason Present
tree pollenearly spring (Feb. - April)
grass pollenlate spring (April - June)
weed pollenfall (late Aug. - Nov.)
mold sporesperennial (year round)

Indoor allergens are present year round. Winter does seem to increase exposure to indoor allergens due to avoidance of outdoor activity and tighter enclosure of the indoor environment. Mold spores, though typically outdoor allergens, can be problematic indoors if persistent moisture due to water leakage or poor construction is present.

  • dust mite
  • animal dander
  • cockroach
  • mold spores

Food Allergy - is different than food intolerance, where the body has difficulty digesting or handling certain food types. Food allergy denotes a specific (IgE mediated) immunological reaction against proteins found within the food. Food allergy may affect up to 8% of the U.S. population and can be separated into Type I and Type II based on the mechanism of sensitization.

Type I food allergy occurs after a primary sensitization event to the implicated food and is more common in children, especially during infancy. The primary sensitization event may occur in the womb do to passage across the placenta of food proteins ingested by the mother. Thus infants may react on first exposure to a food due to sensitization that occurred prior to birth. Many children will outgrow their food allergy by age three, however they may go to manifest environmental allergies between the ages of three and six. Some food allergies like peanut, tree nut and shellfish tend to be lifelong. Symptoms of type I food allergy include acute urticaria or hives, flushing, eczema, vomiting, diarrhea, wheezing, cough, rhinitis and when severe even anaphylaxis.

Foods that account for 80% of type I allergies:

  • Milk
  • Soy
  • Egg
  • Wheat
  • Peanut
  • Fish
  • Shellfish

Type II food allergy occurs after a primary sensitization event to environmental allergens like pollen, dust mite or cockroach. Similar proteins are present both in foods and environmental allergens.

Type II food allergy occurs when it is directed against environmental allergens cross-reacts with similar proteins present within foods. Type II food allergy is more common in adults and children after 5 or 6 years of age, when environmental allergy is more prevalent.

Symptoms of Type II food allergy are typically milder than Type I food allergy due to the cross-reactive nature of the binding event and the fact that the cross-reactive proteins are present in smaller quantities. At times symptoms can be more severe, this usually occurs at times of the year when exposure to the sensitizing environmental allergen is high. For example allergic symptoms from ingestion of oranges may be more severe during grass pollen season than other times of the year (proteins in oranges cross react with grass pollen proteins).

Primary allergen sensitivityFoods implicated in type II cross-reactive allergy
Tree pollenapple, peach, cherry, apricot, plum, kiwi, hazelnut, carrot, celery, potato, fennel seed
Weed pollenmelons, banana, zucchini, cucumber, carrot, celery
Grass pollenmelons, peach, cherry, apricot, plum, kiwi, orange, citrus fruits, potato, tomato, peanut, cereal grains
Dust mite, cockroachshrimp, fish, chicken, beef, pork and other meats

Treatment of food allergy

Treatment of type I food allergy currently is limited to avoidance of the offending foods. The fact that most children will outgrow their food allergy is encouraging and this seems to be hastened by complete avoidance of the offending food. There is some evidence that Type II food allergy can be treated by immunotherapy to the primary sensitizing pollen or environmental allergen. Immunotherapy or allergy shots for type I food allergy has not been shown to be of benefit.

Stinging Insect Allergy

Allergic reactions to stinging insects such as honey bee, yellow jacket, wasp, hornet and fire ant can be life threatening when severe or confined to large local reactions when mild. The diagnosis of stinging insect allergy can be confirmed with blood testing or skin testing for specific IgE. When an allergy is confirmed treatment options include avoidance of the implicated stinging insects, availability of injectable epinephrine (epi-pen) and immunotherapy or allergy shots. Desensitization by allergy shots has been shown to be highly effective in preventing severe life threatening reactions on subsequent sting events.

Drug allergy

Reactions to drugs or antibiotics can take many forms and about 25% of all drug reactions may represent a true immunologic event. Immediate or IgE mediated reactions are some of the most serious events and these can be diagnosed by skin testing with the implicated drug. Testing is limited by the lack of standardized testing materials (except for penicillin) and the fact that many drugs must be metabolized by the body before causing the reaction. Despite these limitations, a careful history combined with diagnostic skin testing can often times confirm or rule out a true allergy to the drug. In some instances the drug can still be administered when a true allergy exists through a desensitization protocol performed in the hospital or office setting.


Aircare Allergy Treatments

Environmental pollens, indoor allergens and mold spores:

Diagnostic Testing: skin prick multi-tester device, intradermal skin tests with both early and late phase reading, skin patch tests and blood testing (Pharmacia Immunocap system).

Treatment: prescription medications, specific avoidance recommendations and immunotherapy/allergen vaccination (both standard and rush/rapid protocols used).

Foods:

Diagnostic Testing: skin prick multi-tester device, fresh food prick-prick method, skin patch tests, blood testing (Pharmacia Immunocap system) and in office food challenges.

Treatment: prescription medications, specific avoidance recommendations.

Stinging insects (hymenoptera, fire ant, mosquito):

Diagnostic Testing: skin prick/intradermal methods and blood testing (Pharmacia Immunocap system).

Treatment: immunotherapy/allergen vaccination (both standard and rush/rapid protocols used).

Antibiotics, biologicals and drugs:

Diagnostic Testing: skin prick/intradermal/patch methods and blood testing (Pharmacia Immunocap system for penicillin and amoxicillin only).
Treatment: avoidance recommendations and in office rapid desensitization protocols.


For more information:

http://www.nlm.nih.gov/medlineplus/allergy.html
http://www.allergicchild.com
http://www.foodallergy.org
http://www.aaaai.org
http://www.medem.com/medlb

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