Immune System
The Common Cold and the Flu
Posted by
admin 22 August, 2008
(2) Comment
The common cold and the flu (influenza) are both caused by viruses. The viruses that cause colds and the flu are transmitted when an infected person coughs or sneezes into the air and another person inhales the infected droplets. You can also catch a cold or the flu by kissing an infected person or by touching your mouth after touching the other person’s hands or an object he or she has touched. Each cold is caused by a different virus, and there are nearly 200 different cold viruses. Adults average about two to four colds per year. The virus that causes the flu changes from year to year; that is why a flu immunization is good for only a year. When these viruses enter your body, they multiply rapidly. Your immune system tries to fight them, producing symptoms that include coughing, sneezing, and a runny nose.
The flu is a viral infection of the nose, throat, and lungs. It is usually mild in young and middle-aged adults but can be life-threatening in older people and people who have a chronic illness such as heart disease, emphysema, asthma, bronchitis, kidney disease, or diabetes. The flu also can lead to more serious, potentially life-threatening infections such as pneumonia. Because pneumonia is one of the five leading causes of death among older people, it is important for older people to take steps to prevent the flu. The best preventive measure is a flu shot, given each fall at the beginning of the flu season. A pneumonia shot is another preventive measure available for older people and people who have a chronic illness; the pneumonia shot is given only once.
Many people confuse the common cold with the flu, but there is one easy way to tell the difference: the flu usually causes a fever, while a cold does not. Also, a cold causes nasal congestion more often than the flu. In general, cold symptoms are milder than flu symptoms and do not last as long.
The flu is very contagious. Symptoms differ from person to person, but common symptoms include weakness, body ache, headache, and sudden fever. The fever can last from 1 to 6 days. People with the flu also have a cough, chills, and reddened, watery eyes. If the flu progresses to pneumonia, symptoms become more severe, and chest pain may occur as the lungs become inflamed. If the pneumonia was caused by a bacterial infection, it can be treated with antibiotics. Antibiotics are not effective for treating viral infections, including the common cold.
There is no cure for the common cold, and many of the over-the-counter remedies available at your local pharmacy (such as pain relievers and decongestants) treat only the symptoms of a cold. Most colds will clear up within a week or so. The usual treatment for the flu is to take aspirin, acetaminophen, or ibuprofen to reduce the fever and body aches, drink plenty of liquids, and rest in bed until after the fever has been gone for 1 to 2 days. Antiviral medications such as amantadine, rimantadine, zanamivir, and oseltamivir are available by prescription to prevent and treat many types of influenza.
Categories : Immune System
Warning Signs of Food Allergy
Posted by
admin 22 August, 2008
(3) Comment
If you have a food allergy, your immune system mistakenly regards a particular food as harmful and begins producing antibodies to that food. Each time you eat that food, your immune system releases various chemicals to protect your body. These chemicals produce symptoms that can affect your airways, skin, or intestinal tract. Symptoms of food allergy can include:
• skin reactions such as hives or rashes
• nasal congestion
• nausea, diarrhea, or gas
• shortness of breath, or asthma attacks in people who have asthma
If the reaction is severe, you may experience life-threatening symptoms within minutes of eating. A severe allergic reaction can rapidly cause difficulty breathing, lowered blood pressure, and loss of consciousness (see “Anaphylactic Shock,” post). If you or a person you are with has these symptoms, seek emergency medical help immediately.
Categories : Immune System
Allergies to Food
Posted by
admin 22 August, 2008
(1) Comment
A food allergy is a reaction of the immune system to a food or food ingredient that most people find harmless. If you eat a food that produces an allergic reaction, your immune system responds by releasing numerous chemicals that cause allergic symptoms. A food allergy is different from a food intolerance, which does not trigger an immune response. A food intolerance (such as lactose intolerance) usually arises from an enzyme deficiency and produces symptoms such as stomach cramps, gas, or diarrhea. Food intolerances are relatively common, but a true food allergy is rare, affecting only about 1 percent of the population.
The most common foods that cause allergies in adults are fish and shellfish, eggs, and nuts—such as peanuts, walnuts, and pecans. Symptoms of food allergy can include skin reactions such as hives or rashes, nasal congestion, asthma attacks in people who have asthma, and gastrointestinal problems such as nausea, gas, or diarrhea. Because both food allergies and food intolerances can cause intestinal symptoms, the two disorders are easily confused and must be diagnosed by a doctor.
Food allergy symptoms can appear immediately after eating or may develop over time—within hours or even days. In severe cases the food can provoke a serious reaction known as anaphylaxis (see “Anaphylactic Shock,” Post), which can be life-threatening. Signs and symptoms of anaphylaxis include hives, difficulty breathing, a drop in blood pressure, and loss of consciousness.
To determine whether you have a true food allergy, your doctor probably will perform one of two tests: a skin prick test or a blood test called the radioallergosorbent test (RAST). During the skin prick test, the doctor deposits a small amount of the suspected food allergen onto your forearm and then pricks the skin beneath it with a needle. A small red bump will appear at the site if you are allergic to that particular food. For the RAST, a sample of your blood is taken and sent to a laboratory for analysis to determine whether your body has formed antibodies to the food in question. Your doctor also may ask you to record everything you eat in a food diary for a couple of weeks to help in the diagnosis.
Many people will outgrow food allergies, except allergies to nuts, fish, and shellfish. The best treatment for a food allergy is to avoid eating the food that causes the allergic reaction. You will need to read food labels carefully and ask questions when dining out to make sure that the foods you eat do not contain the allergen. Severe allergic reactions are life-threatening. If you have had a previous severe allergic reaction, you will need to carry an injecting device that contains epinephrine with you at all times, so you can inject yourself immediately if you have another allergic reaction.
Categories : Immune System
Warning Signs of Allergy to Medication
Posted by
admin 22 August, 2008
(0) Comment
Always report any unpleasant or unexpected side effects of medication to your doctor.
The following symptoms may indicate an allergy to medication:
• rash
• hives (itchy, raised, red patches on the skin)
• itching
• swollen lips
If you experience any of these symptoms after taking medication, contact your doctor. If you experience more serious symptoms—such as nausea and vomiting, difficulty breathing, confusion, loss of consciousness, swollen tongue or throat, or slurred speech—seek emergency medical help immediately. A severe allergic reaction is a medical emergency that can lead to respiratory failure and shock (see “Anaphylactic Shock,” Post).
Categories : Immune System
Anaphylactic Shock
Posted by
admin 22 August, 2008
(0) Comment
Anaphylactic shock is a severe, life-threatening allergic reaction. The reaction usually occurs after an insect sting or bite or after injection of a specific drug such as penicillin. Occasionally the reaction occurs after eating a particular food or taking a specific medication. Anaphylactic shock is a medical emergency that requires immediate medical treatment.
During an anaphylactic reaction, the body releases massive amounts of histamine and other powerful chemicals in response to the presence of the allergen. The blood vessels widen, causing a sudden, severe decrease in blood pressure. Other symptoms can include hives (itchy, raised, red patches on the skin); swelling of the lips, tongue, and throat; abdominal pain; diarrhea; and difficulty breathing due to bronchospasm (narrowing of the airways in the lungs).
If you or someone you know has an anaphylactic reaction, call 911 or your local emergency number. While waiting for emergency help to arrive, have the person lie down, with face up, head low, and legs raised about a foot high to improve blood flow to the upper body. An injection of epinephrine is needed as soon as possible to counteract the allergic reaction. If you or the person has had a severe allergic reaction before and carries an injecting device that contains epinephrine, use it as soon as symptoms appear.
Categories : Immune System
Allergies to Medications
Posted by
admin 22 August, 2008
(0) Comment
Drug allergies arise from a complicated response by the immune system to a specific medication. A person usually goes through three stages when developing an allergy to a medication. First, he or she must be exposed to the drug by taking one or more doses. Next, the person’s immune system identifies the drug as harmful and begins producing antibodies to fight it. Finally, the person takes another dose of the drug, and the allergy symptoms appear. The symptoms may appear immediately, within 1 to 2 hours, or within a few days to a week after taking the drug. Common symptoms of drug allergy include skin rash or hives, difficulty breathing, and itching. Severe drug allergies may cause seizures, loss of consciousness, or shock. If you have had a previous severe allergic reaction, you will need to carry an injecting device that contains epinephrine with you at all times, so you can inject yourself immediately if you have another allergic reaction. An injection of epinephrine can save your life.
Medications that typically produce an allergic reaction include antibiotics (such as penicillin), sulfa drugs, insulin that contains pig or ox protein, vaccines, and aspirin. If you are allergic to any medications, be sure to tell your doctor and other healthcare providers who are treating you, such as a nurse or a dentist. Also, in case of emergency, you should always wear a medical identification bracelet or necklace and carry a wallet card that informs people of your allergy. This will help ensure appropriate medical treatment.
Categories : Immune System
Airborne Allergies
Posted by
admin 22 August, 2008
(1) Comment
An allergy is an exaggerated or inappropriate response of the immune system to a substance that is harmless to most people. Substances that can cause such reactions are called allergens. Common allergens include pollen, dust particles, certain foods, insect venom, mold, and medications. Doctors think that the reason some people are allergic to a particular substance is because they have inherited a tendency to be allergic (although not necessarily to that particular substance). Being exposed to a potential allergen when the body’s defenses are lowered or weakened—such as during a viral infection—seems to contribute to the development of an allergy. People with allergies are often sensitive to more than one allergen.
During an allergic reaction, the immune system is responding to a false alarm. When a person comes into contact with an allergen, the immune system launches an inappropriate immune response by releasing large amounts of an antibody (a disease-fighting protein) called immunoglobulin E. Each time the person encounters an allergen, these antibodies signal the body to produce powerful chemicals, such as histamine, that travel to where the allergen is located (such as the airways, the skin, or the surface of the eye) and cause inflammation. Symptoms of inflammation include redness, swelling, pain, and warmth. When pollen, dust, or other airborne allergens cause inflammation of the mucous membrane that lines the nose, the condition is known as allergic rhinitis. Common symptoms include runny nose, coughing, nasal congestion, and sneezing.
One of the most common allergies is pollen allergy. Each spring, summer, and fall, trees, weeds, and grasses release tiny particles called pollen, which ride on currents of air. The pollen enters the nose and throat, triggering allergic reactions in susceptible people. Among North American plants, weeds, especially ragweed, are the most prolific producers of pollen. In fact, the popular term “hay fever” typically refers to allergy to ragweed pollen. Other important pollen-producing weeds include sagebrush, redroot pigweed, tumbleweed, and English plantain. Trees that produce allergic pollen are oak, ash, elm, hickory, pecan, box elder, and mountain cedar. Although a wide variety of grasses grow in North America, only about seven types produce pollen that causes allergic responses.
Each plant has a pollinating period that is the same from year to year. The relative lengths of night and day seem to be the trigger for pollination, so the farther north you live, the later (and shorter) the pollinating period and the later (and shorter) the allergy season. A pollen count measures how much pollen is in the air at a given time. Pollen counts tend to be highest early in the morning on warm, dry, breezy days and lowest on chilly, wet days. If you have allergic rhinitis, try to stay indoors as much as possible on high-pollen-count days, especially in the morning. If you work outdoors, wear a face mask that filters out pollen. If possible, take your vacation at the height of pollen season and go to a location, such as the beach, where pollen counts are minimal.
House dust probably is the most common cause of airborne allergies, producing symptoms of allergic rhinitis. House dust is a mixture of potential allergens. It often contains fabric fibers, cotton lint, feathers and other stuffing materials, bacteria, mold, food particles, bits of plants and insects, and dust mites (microscopic insects). Dust mites live in bedding, upholstered furniture, and carpets. They thrive in summer, and they can live all year in warm, humid houses. The mites produce waste-containing proteins, which are the actual causes of the allergic reaction. Waste products of cockroaches also are are an important cause of allergy symptoms in infested households, especially in urban areas.
If you have a dust allergy, take the time to dustproof your home, especially your bedroom. Eliminate as many dust-gathering and dust-producing items— such as wall-to-wall carpeting, blinds, down-filled blankets, feather pillows, forced-air heating vents, pets, and closets full of clothing—as you can. Encase your mattress in a zippered, plastic, dustproof cover. Wash all of your bedding once a week in water hotter than 130 degrees Fahrenheit. Frequently wipe with a damp cloth all surfaces where dust accumulates.
Many people are allergic to animals, particularly household pets. Pet allergy is not triggered by the dander or hair of dogs or cats but rather by proteins in their saliva, which they transmit to their hair through licking. An animal allergy can take 2 or more years to develop and may not subside until 6 or more months after contact with the animal has ended. The best way to avoid an allergic reaction is to stay away from animals—even if it means finding a new home for a beloved pet. To decrease the level of cat allergens, try bathing the cat weekly, which neutralizes the protein on the fur. And keep the animal out of the bedroom.
Mold is a type of fungus that grows seasonally and causes allergic reactions in some people. Mold levels peak in late summer but, in warmer climates, molds thrive all year and can cause allergic symptoms year-round. Molds can be found wherever there is moisture. Outside, they grow on rotting logs and decomposing leaves. In the house, molds thrive in basements, bathrooms, damp closets, refrigerator drip trays, houseplants, air conditioners and humidifiers, garbage cans, mattresses, and old foam rubber pillows. When inhaled, tiny mold spores often evade the protective mechanisms of the nose and upper airways and reach the lungs. There they can cause bronchospasm (temporary narrowing of the airways in the lungs) or trigger an asthma attack in a person who has asthma.
To minimize your contact with allergy-triggering molds, have someone else mow your lawn and rake leaves, or wear a tight-fitting mask when you do these chores. Clean and disinfect your bathroom fixtures regularly, and be sure to air out closets, mattresses, pillows, and garbage cans. Regularly clean your airconditioner filter and your humidifier filter and water reservoir according to the manufacturer’s instructions. A dehumidifier can help dry out your basement, but you must clean the machine frequently to prevent mold buildup.
In addition to sneezing, coughing, runny nose, and nasal congestion, people with allergic rhinitis also may have itchy, watery eyes and conjunctivitis (an inflammation of the lining of the eyelids). Dark circles typically appear under the eyes, caused by increased blood flow near the sinuses. Some people with allergies may develop asthma, a serious and potentially life-threatening respiratory disorder that causes tightness in the chest, wheezing, and sometimes severe shortness of breath.
Your health history is an important tool that can help your doctor diagnose a potential allergy. While taking your medical history, he or she can determine whether your symptoms recur at the same time each year, which suggests a seasonal allergen such as pollen. The doctor also will ask questions to determine what substances seem to trigger your allergies. To confirm this information, the doctor may perform skin testing, in which tiny amounts of suspected allergens are applied to, injected under, or scratched onto the skin. A small, reddened area will appear in the area where any substance to which you are allergic was applied. Blood tests also may be performed to detect blood levels of antibodies to a specific allergen.
Doctors generally recommend three approaches to the treatment of allergies: avoidance, medication, and allergy injections. For some people, complete avoidance of an allergen such as pollen or mold may require moving to a location where the allergen does not grow. Others may need to give up a favorite pet. If you have allergies, you may not be able to completely avoid the substances that provoke an allergic reaction. That is why doctors try to control allergic symptoms with medications, sometimes in combination. The most common medications prescribed for this purpose include antihistamines, which counter the effects of histamine, the inflammation-inducing chemical released by the body during an allergic reaction. Nasal corticosteroids, which are sprayed into the nose, combat inflammation, swelling, and mucous secretion. Another nasal spray, called cromolyn sodium, prevents allergic reactions from starting. Effective antihistamines and decongestants also are available over the counter. Ask your doctor for recommendations.
Taking a series of allergy injections (immunotherapy) is the only method of reducing your allergy symptoms over the long term. This treatment usually is given over the course of 2 or 3 years. The doctor injects you with gradually increasing doses of the allergen. In response, your body decreases production of antibodies to that substance and begins producing protective antibodies instead. About 85 percent of people with allergic rhinitis experience a substantial reduction in their symptoms within 2 years of beginning their allergy injections.
Categories : Immune System
Immunodeficiency Disorders
Posted by
admin 22 August, 2008
(0) Comment
A weakened immune system can be congenital (present from birth), or it may result from an inherited disorder or an infection. It also may occur as a side effect of drug treatment. People with weakened immune systems have difficulty fighting infections that are easily handled by a healthy immune system. When a person’s immune system is ineffective, harmful microorganisms can thrive and multiply rapidly, causing life-threatening infections.
A small number of infants are born with defects in their immune systems. Infants born with defective B lymphocytes are unable to produce antibodies and therefore are vulnerable to a wide variety of infections. Doctors treat this type of disorder with injections of live antibodies. Some infants lack T lymphocytes because they were born without a thymus gland or because the thymus gland is small and abnormal. This disorder requires a thymus gland transplant. In very rare cases, infants are born without an immune system, a condition known as severe combined immunodeficiency disease. Children with this disease gained notoriety by living for years in germ-free rooms or “bubbles.” A few of these children have been successfully treated with bone marrow transplants.
The best-known immunodeficiency disorder is acquired immunodeficiency syndrome (AIDS), which is caused by the human immunodeficiency virus (HIV). AIDS often leads to various otherwise rare diseases, such as Pneumocystis carinii pneumonia and Kaposi’s sarcoma (a form of cancer). These diseases are called opportunistic diseases because they rarely occur in people with healthy immune systems, but occur more in people with weakened immune systems, in whom conditions for development are favorable. HIV infection also damages the central nervous system (the brain and the spinal cord), which leads to dementia (progressive deterioration of mental functioning).
HIV infection may cause no symptoms in the early stages or can produce flulike symptoms, including fever, chills, fatigue, sweating at night, and a dry cough. Other symptoms include sudden unexplained weight loss and chronic diarrhea. Although some infected people may have no symptoms, they still can transmit the virus to others.
HIV is transmitted by sexual contact or by direct contact with infected blood or body fluids. HIV can be transmitted from an infected woman to a fetus during pregnancy or to an infant during childbirth or through breast milk. HIV also can be transmitted by sharing needles during intravenous drug use. In the past, some people were infected with HIV through blood transfusions or contaminated blood products. Today, however, all donated blood is routinely screened for HIV, and the blood supply in the United States is safe.
At present there is no cure for AIDS. Early diagnosis and treatment are vital. Certain medications that are currently available, when used in combination, seem to slow development of the disease. These medications include nucleoside analog reverse transcriptase inhibitors (such as zidovudine, also called AZT), which interrupt an early stage of virus replication, and protease inhibitors (such as indinavir, ritonavir, and saquinavir), which interrupt the same process at a later stage. Although these “cocktail” drug regimens typically cause unpleasant side effects such as nausea and diarrhea, when started early, they are enabling many people infected with HIV to live longer, more productive lives. Other drugs designed to combat the virus, bolster the immune system, and prevent or treat opportunistic infections that result from HIV infection are now being tested. Research on an AIDS vaccine is also under way.
Immunodeficiency can be an unwanted side effect of certain medications, such as those used to treat cancer. Anticancer drugs used during chemotherapy affect cells that divide rapidly, including the white blood cells (lymphocytes) that fight infection. Because of this, people undergoing chemotherapy may become more susceptible to opportunistic infections.
Categories : Immune System
