Dangerous mites

i.1 - Allergy

Allergies are incredibly common. Some figures report that 20% of the population suffer from allergic diseases at some point of their life. Inheritance has a major influence on allergy. If one parent has allergies, the odds are that one in three of the children will have allergies. If both parents have allergies, then all the children will probably have allergies. Aside from inheritance, it is not known why some people get allergies and others do not. Some believe that hormonal influences, viral infections, smoking, and a number of other influences affect whether one develops allergies. No one knows all the reasons why people with equal likelihood to develop allergies become allergic to different things, or why some have hay fever and other have asthma. Second, a person has to be exposed to an allergen, a foreign protein that causes allergy. Ragweed pollen is the major cause of allergy in the United States, grasses and mites in Europe.

Worldwide, however, the major allergens is the dust mite, Dermatophagoides pteronyssinus. All temperature climate areas in the world have dust mites, which live in carpeting, mattresses, and upholstery. They have to have a temperature in their homes above 60 degrees all year. Dust mites also need a relative humidity above 50 percent. People are not actually allergic to its feces. The fecal balls are sticky, heavy materials that bind to carpeting or upholstery. One of the worst ways to bring dust mite allergens into the air is to vacuum the floor; this blows the dust up into the air, where it floats for a couple of hours and makes up the moats in a beam of sunlight.

There are three components to allergies: mast cells, which contain chemical like histamine; antibodies, a specific type of protein made by the immune system, known as IgE; and allergens, which trigger the reaction. Mast cells are the allergy-causing cells and are found in every tissue throughout the body, though they are most heavily concentrated in those tissues that are exposed to the outside world-the skin, linings of the nose andd lungs, gastrointestinal tract, and reproductive system. The IgE antibody, which actually causes allergy, sits on the surface of these mast cells. A mast cell has about 1,000 histamine-containing granules in its cytoplasm, and on its surface are between 100,000 and 1 million receptors for IgE. When the IgE encounters the allergen, it triggers the mast cell to release granules from it's cytoplasm. Those granules contain histamine and other chemicals. These mediators that are released then interact with the tissues, causing the allergic symptoms. When a mite's allergen gets in the skin that lines the inside of the nose, those enzymes are released from the mite' particle grain and work their way through the mucus in the nose. The enzymes sensitize the person by initiating the production of IgE antibodies, which then sensitize mast cells that are in the nose. It generally takes about two to five seasons of allergen exposure before a person makes enough IgE to result in allergy symptoms. Everyone makes some IgE. Only people with genetic predispositions toward allergies make large quantities. IgE, like other antibodies that the body produces, is part of the body's defense mechanism. Some antibodies, like IgG, get rid of Streptococcus and help cure those infected with a strep throat. Other antibodies get rid of cold viruses. The IgE antibody is directed against parasites. Its function is to protect the body against parasitic infections. There are few parasites in the United States, but the IgE antibody system reacts against the enzymes from the surface of pollen grains as if they were parasites and elicits an allergic response. The body is misdirecting an extremely important immune response at pollens, dust, dander, and molds. Most antibodies last in the body about three weeks, but IgE may sit on its receptor on mast cells and sensitize the mast cells for years. For example, someone who had an adverse allergic reaction to penicillin as a child could still be allergic to the drug as an adult. The IgE antibody the person made as a 6-year-old child would still be present in the 40-year-old adult. It is sitting on the mast cells, which are long-lived cells, and it conveys incredibly long-lived sensitivity to allergens. In one research study, we looked at mast cell histamine release under the electron microscope. We sensitized a mast cell to IgE, making it allergic to grass, trees, ragweed, and certain breed of cats and dogs. We then took this mast cell and exposed it to an extract of ragweed. Over a 15 minute period, many of the granules in its cytoplasm disappeared. Fifteen minutes later, the granules were all gone. Although the mast cell had no visible secretory granules in its cytoplasm, it was alive and well; over the next 6 to 24 hours it would reconstitute all the granules that had disappeared. After releasing histamine from its granules, a mast cell can once again do damage to the person the next day when he or she breathes in ragweed. The chemicals that are released from mast cells are the mediator that cause allergies. At last count, there were 28 separate chemicals released by mast cells that orchestrate allergic responses.

The allergic symptoms a person experiences depend on the tissue in which the mediators released. For example, if these chemicals are released in the nose, the person will get hay fever, allergic rhinitis. If they are released in the chest, the person will get asthma or coughing. Chemicals released in the skin will produce hives or eczema, in the intestine will produce food allergy or diarrhea, and in the brain may result in a migraine. There is a whole spectrum of problems that these mediators can cause. Allergic reactions often take place very quickly. Those who experience allergy may go outside on a bright, sunny, windy morning during the ragweed season and within 15 minutes begin to have allergic reactions. This reaction is referred to as immediate hypersensitivity. When mast cells release their chemicals, they cause immediate reactions. Some people also experience late-phase reactions. When mast cells release their chemicals, they cause an inflammatory response. The site of the allergic reaction gets red, swollen, hot, and tender, causing a more prolonged response. A person may go out at 8 a.m. and experience a late reaction at 4 p.m. Such reactions may last one day, two days, one week, or one month from a single allergens exposure. They are part of the underlying problem for chronic asthma, rhinitis, eczema, hives, and other allergic diseases.

Diagnosis

People with allergy symptoms, such as the runny nose of allergic rhinitis, may at first suspect they have a cold ... but the "cold" lingers on. It is important to see a doctor about any respiratory illness that lasts longer than a week or two. When it appears that the symptoms are caused by an allergy, the patient should see a physician who understands the diagnosis and treatment of allergies. If the patient's medical history indicates that the symptoms recur at the same time each year, the physician will work under the theory that a seasonal allergen (like pollen) is involved. Properly trained specialists recognize the patterns of potential allergens common during local seasons and the association between these patterns and symptoms. The medical history suggests which allergens are the likely culprits. The doctor also will examine the mucous membranes, which often appear swollen and pale or bluish in persons with allergic conditions.

a) Skin Tests

Doctors use skin tests to determine whether a patient has IgE antibodies in the skin that react to a specific allergen. The doctor will use diluted extracts from allergens such as dust mites, pollens, or molds commonly found in the local area. The extract of each kind of allergen is injected under the patient's skin or is applied to a tiny scratch or puncture made on the patient's arm or back. Skin tests are one way of measuring the level of IgE antibody in a patient. With a positive reaction, a small, raised, reddened area (called a wheal) with a surrounding flush (called a flare) will appear at the test site. The size of the wheal can give the physician an important diagnostic clue, but a positive reaction does not prove that a particular pollen is the cause of a patient's symptoms. Although such a reaction indicates that IgE antibody to a specific allergen is present in the skin, respiratory symptoms do not necessarily result.

b) Blood Tests

Although skin testing is the most sensitive and least costly way to identify allergies in patients, some patients such as those with widespread skin conditions like eczema should not be tested using that method. There are other diagnostic tests that use a blood sample from the patient to detect levels of IgE antibody to a particular allergen. One such blood test is called the RAST (Radio Allergo Sorbent Test), which can be performed when eczema is present or if a patient has taken medications that interfere with skin testing.

c) Spirometry

An allergist will do spirometry to measure the patient's ability to blow air out of the chest. The patient takes a deep breath and blows into a machine called a spirometer. The doctor then measures how much and how quickly air was blown out. Most people blow all the air in their chest out within 3 seconds; 75 percent of the air is exhaled within 1 second. The point of maximum expiration is called the "peak flow". Asthmatics have trouble blowing out the air. That is because of airflow obstruction during breathing out. As a result, they have very hard time blowing out air and it takes much longer. Over the past few years, the availability of inexpensive and accurate peak flows meters has made life easier for doctors. Patients can measure their peak flow in the morning and evening. The patient blows into the flow meter and it measures the peak expiratory flow rate.

Common diseases: Bronchial asthma, Allergic rhinites, Anaphylactic shock, Atopic dermatitis

Therapy

In spite of all the recent advances in the field of allergy and immunology there are still only three basic methods of treating an allergy.

a) Avoidance - Environment

The first and most important principle of therapy is avoidance or environmental controls.Environmental controls are the measures that would eliminate the patient's exposure to the offendingagents. For example, if a patient were allergic to dust he should prepare a dust-free environment in his bedroom. This would mean that he should pick up the wall-to-wall carpet and leave a bare floor. He should remove any kind of stuffed furniture or stuffed animals from the room. He should remove any old books, newspapers and stored clothes in the closets. All these measures would aid in decreasing the patients exposure to dust and the accumulation of dust in the bedroom. Environmental controls are the most important component of therapy. In many cases, if a patient can eliminate his exposure to an allergen his symptoms will decease markedly and there is no need for further forms of treatment.

b) Medication

The second mode of therapy is medication. Medication is also an important form of therapy and in some patients such as asthmatics it is essential. In recent years the field of allergy and immunology has provided newer and better medications which make a more complete control of the allergic patient possible. However, in most situations medications just treats the tip of the iceburg. It relieves or alleviates symptoms but it does not address the cause of the problem. Nevertheless, in many patients medication and environmental controls are enough to relieve the patient adequately so that no further treatment is necessary.

c) Hyposensitization- Immunotherapy

The third form of therapy is hyposensitization, otherwise known as immunotherapy or "shots". Hyposensitization is the process of injecting small amounts of the antigen or allergens to which the patient is allergic. These allergens are the materials which cannot be avoided such as dust, pollens, and molds. They are injected periodically into the skin of the allergic patient in an attempt to induce the development of so-called blocking antibodies. These blocking antibodies serve to block the reaction between the allergic patient and the thing he is allergic to. In general, the longer the patient has received immunotherapy the more blocking antibodies he makes. Eventually the injection therapy can be tapered off and the blocking antibodies will remain in the system and result in a greater tolerance of the allergic patient to the materials that he was allergic to. Shot therapy does not cure allergies but only tend to raise the person's tolerance level and thereby decrease his symptoms after he is exposed to the antigens.

Allergenic mites

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