Allergy facts
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Allergies occur through a process of sensitization and reaction. During sensitization, exposure to an allergen leads to the production of IgE antibodies that attach to mast cells. In the early phase reaction, re-exposure to the allergen causes it to attach to these IgE antibodies, activating mast cells and basophils to release inflammatory mediators causing sneezing, itching, and more. The late phase reaction occurs hours later through the actions of recruited cells. Chronic allergies can develop through priming and hyperreactivity. Common triggers include dust mites, animals, pollens, molds, foods, and irritants like smoke. Avoiding triggers and using medications or immunotherapy can help manage allergy
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Allergy facts
- 2. PATHOPHYSIOLOGY • Sensitization • Early (acute) phase reaction • Late phase reaction • Chronic disease
- 3. SENSITIZATION • Previous exposure • Produce IgE antibodies • IgE antibodies attach to mast cells in tissues –Eye, nose, lung, skin, GI tract
- 4. EARLY PHASE REACTION • Allergen attaches to IgE on mast cell • Release of mediators – Act on nerves, blood vessels • Production of mediators – Continue actions on blood vessels, nerves – Recruit inflammatory cells • Sneeze, itch, runny nose, stuffy nose
- 5. LATE PHASE REACTION • 2-8 hours after initial reaction • Same symptoms as early reaction • Release of mediators from recruited cells • Related to severity of early reaction
- 6. CHRONIC DISEASE • Priming – Need less allergen to trigger symptoms • Hyperreactivity – Symptoms from exposure to strong or irritating fumes or odors • Inflammation – Ongoing symptoms
- 7. ALLERGIC TRIGGERS • Dust mites –Carpeting, upholstered furniture • Animals –Furry or feathered • Pollens –PE, recess
- 8. ALLERGIC TRIGGERS II • Cockroaches • Molds – Water damage, leaking roofs, poorly maintained heating/cooling systems – Outdoors and indoors • Foods – Uncommon for chronic symptoms
- 9. NONALLERGIC TRIGGERS • Strong odors from cleaning agents, floor finishing agents, pesticides, fertilizer, etc • Cigarette smoke • Chalk dust • Dry erase pens
- 10. THERAPY • Avoidance of triggers • Medications • Allergy injections
- 11. AVOIDANCE OF TRIGGERS • No carpeting or upholstered furniture • No furry or feathered pets • Perform maintenance chores requiring use of irritating chemicals/cleaners when children not present • Maintain heating/cooling systems • No smoking
- 12. ALLERGY INJECTIONS • When medications and avoidance don’t work • Usually prescribed by a specialist • Effective for dust mites, cats, pollens – When history confirms skin test results • More properly called immunotherapy
- 13. Additional Resources • Allergy & Asthma Network/Mothers of Asthmatics, Inc. -- http://www.aanma.org • American Academy of Allergy, Asthma, and Immunology -- http://www.aaaai.org • American Academy of Pediatrics -- http://www.aap.org • American College of Allergy, Asthma, and Immunology -- http://www.allergy.mcg.edu
- 14. Additional Resources • Asthma & Allergy Foundation of America -- http://www.aafa.org/home • US Environmental Protection Agency -- http://www.epa.gov/iaq
Editor's Notes
- The allergic process begins with sensitization, which will be covered in a subsequent slide. Regardless of the organ involved, the allergy reaction consists of an acute reaction, which happens shortly after the exposure to the allergen, a late phase reaction that can occur 3-8 hours after the acute reaction, and chronic disease. Most patients have an acute reaction. Only about half the patients will have a late phase reaction, and it usually follows a more severe acute reaction. Chronic disease does not always occur, if the exposure to the allergen is limited. Continued exposure usually results in chronic disease.
- Sensitization refers to the process where children with a genetic tendency to develop allergy begin to respond to exposure to an allergen by making a special antibody, called IgE. This IgE is specific for the allergen. Once the IgE is made by the immune system, it attaches to special cells in the tissues of various organs, called mast cells. Organs that contain mast cells include the eye, nose, respiratory tract, skin and GI tract.
- This reaction occurs shortly after allergen exposure. Once there are enough IgE antibodies attached to the mast cell, then further exposure to that allergen can result in interaction between the allergen and the IgE antibody on the surface of the mast cell. This interaction results in the release of several different types of chemical from the mast cell, called mediators. These mediators act on nerves, blood vessels, and other cells. The mediators that act immediately on the blood vessels and nerves (and muscles in the airway) cause such symptoms as sneezing, itchy and runny nose, and stuffy nose. Some of the mediators act to recruit other cells into the tissues, which are involved in late reactions.
- In some patients, symptoms very similar to the early phase symptoms occur again 3-8 hours later. This doesn’t occur in every case, but tends to be more likely when the early reaction is severe. It is caused by the release of mediators from cells that are recruited into the tissues, by some of the mediators released by the mast cells.
- The cells that are recruited into the tissues release mediators of their own, which causes damage to the tissues, or inflammation, and recruits even more cells into the tissues. This causes “priming” of the tissues, which means that they now react to even smaller doses of allergen. This is why patients with hay fever continue to have symptoms, even when the pollen count is low. The inflammation also causes the patient to react to non-allergens, such as strong odors or perfumes. If the exposure to the allergen continues, this causes a chronic inflammation in the tissues and the symptoms continue to occur.
- There are many different allergens that can trigger reactions. This slide lists the more common allergens, and where the exposure occurs. Dust mites are one of the most common allergens, worldwide. They are present indoors, and are very sensitive to humidity and heat. They grow best in warm, humid environments (indoors in warm or temperate climates) but do not grow well in very dry climates. For most children. Carpeting and the surface of mattresses and pillows are the major source of exposure. Any furry or feathered pet can be an allergic trigger, but cats and dogs are the most common, because they are the most common household pets. Cats produce more allergen that dogs, and so are more “allergenic”. The allergen in the dog is present in the hair and skin, and it does not matter how long the hair is. In cats, the allergen is present in secretions from the skin and in the saliva. It is on the hair, because the cat is always grooming itself, but it is not the hair. Pollens are encountered primarily outdoors. Tree pollens tend to be present in the early spring, grass in the late spring and early summer, and weed pollens in the late summer and early fall. In very warm climates, the pollen can be present for longer periods of time.
- Cockroaches are common allergens in the inner city. They can be present wherever food or garbage is left out, however. Molds are usually an outdoor allergen, and can be a particular problem in the midwest and southeast US during the summer, when the weather is hot and humid. Molds become an indoor problem only when there is a moisture problem as listed on the slide. Foods can cause acute allergic reactions, but are uncommon causes of chronic allergy symptoms.
- When a person has inflammation occurring in the nose or lungs from chronic allergen exposure, these substances can aggravate symptoms.
- Therapy of allergy always involves avoidance of the allergen, whenever possible. This can result in improvement in symptoms and less need for medications. Total avoidance is usually not possible, so medications play an important role in the management of allergic disease. Allergy injections can be very effective treatment for some allergic conditions, and are usually used when avoidance and medications are not effective in relieving symptoms.
- This slides lists some things that can be done in a school setting to reduce exposure to common allergens
- Allergy injections are only useful when the symptoms correspond to an exposure to an allergen the patient has shown sensitivity to, usually by skin testing. Allergy injections should be prescribed by someone with training and experience in allergy.