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Allergic individuals inherit the gene from one of the parents or both. If one parent has allergies, the child has a 40% chance of developing allergies; if both have allergies, the child has 70 – 90% chance of developing allergies. The allergy gene alone does not cause reaction. To react, the individual has to have the gene and be in the right environment. Gene-environmental interaction leads to allergic reaction. The prevalence of allergic diseases in the developed world is partially explained by the hygiene hypothesis which stipulates that allergies are due to too much cleanliness. The hypothesis states that in the developing world where individuals are frequently exposed to bacteria, the immune system is busy fighting the bacteria. However, in the developed world where children are not much exposed to bacteria, the immune system , ``that is looking for work”, turns to fight innocuous substances such as pollen and other allergens. There are three diseases that go together and are called atopic diseases: Atopic dermatitis (Eczema), Asthma and allergic Rhinitis. There is something called the atopic march in which children start with Eczema and if they get an RSV infection they come up with their first wheeze that may continue until adulthood or subside early in childhood, and by age 2 most children develop the allergic rhinitis. Sometimes, the sequence is eczema-allergic rhinitis-asthma. Food allergy is a fourth entity that may go along with these three atopic diseases. Food allergy often contributes to the exacerbations of atopic dermatitis and when that is discovered, elimination of the food in the child’s diet helps alleviate the atopic dermatitis problem.
The process of sensitization starts with exposure of the allergen to Th0 cells that differentiate into Th2 cells instead of Th1. Th1 cells are specialized to fight bacteria. Once the Th2 cells are formed, they produce IL-4 and IL-13 (IL=Interleukens, chemicals that white blood cells use to communicate) that stimulate the B-Cells to produce IgE. Once the IgE is formed, it circulates in the blood and finds its receptors on two white blood cells: mast cells that live in the skin and tissues and Basophils that live in the blood itself. These cells have the IgE receptors. Once the IgE finds its receptors, it binds them. At that point, these misery cells, because they make millions of people miserable around the world, are armed and dangerous and waiting for the next encounter. When the individual is exposed to the same allergen again, the allergen goes through the nose and eventually makes its way to the blood system and find the IgE’s that are already on the surface of the two cells and binds them. A cross-linking of the molecules occurs and that signals to the cells to pour out their granules (degranulation). The first chemical granule that is released is histamine. Histamine is a nerve ending irritant and causes itching. The individual therefore experiences, itchy eyes, itchy nose, itchy throat, sneezing and runny nose. To treat these symptoms, antihistamines such as Benadryl, Claritin, Clarinex, Allegra and Zyrtec are given. Zyrtec is one of the best antihistamines that have come over the counter since January 2008 and that can help the histamine problems. The reason for discontinuing antihistamines for skin testing is that histamine is the positive control and saline the negative control. Antihistamines therefore will blunt the positive control and the results will be negative.
If histamine had been the only chemical released by mast cells and basophils, the allergy solution will be simple. Use antihistamines and there will be no more symptoms. However, there are many other chemicals produced by the misery cells. Two of these chemicals, Leukotrienes (LTC4) and Prostaglandins tend to cause a late phase allergic reactions: stuffy nose, postnasal drip, coughing, and for asthmatics, constriction of the airways and therefore wheezing. To block the Leukotrienes, Montelukast and other Leukotriene receptor antagonists were conceived and Singulair is the most popular. Children and adults who have allergic rhinitis and asthma symptoms should therefore use a combination of a good antihistamine such as Zyrtec and a good LTRA such as Singulair. The master blocker of all these chemicals released by the misery cells is steroids and that is why many physicians inject cortisone or give prednisone to their patients when they present with allergy symptoms. Systemic steroids however, have multiple undesirable effects in both adults and children and reserved only for short term bursts for brittle asthma or other severe inflammation. For the treatment of allergic rhinitis, nasal corticosteroids that act locally are desirable and they are: Flonase, which is off patent and therefore veramyst is now on the market . Nasonex, which has the same potency as flonase is most desirable in children and is approve for children two years old and above. Flonase, veramyst as well as Omnaris (Ceclosenide) are approved for children over 4 years. Budesonide (Rhinocort AQ ) is also approved for pregnant women with allergies. Treatment for allergic diseases therefore requires combination therapy: antihistamines to block the histamine released from mast cells and basophils, LTRA to block the Leukotrienes and nasal corticosteroids to block all the chemicals that participate in allergic reactions.
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