Allergic reactions Diagnosis

  • Diagnosis

    Allergic reactions are serious and potentially life-threatening, and can cause injury to tissues throughout the body. Some people have hypersensitive immune systems that overreact to otherwise harmless things such as bee stings, foods, medications, and latex. Reactions range in severity: one person may break out in hives after eating shrimp; another may feel his or her throat closing up. In some cases, the person might pass out or have a heart attack. Without immediate medical treatment, allergic reactions can be fatal.

    Allergic reactions involve proteins called antibodies that react to foreign substances called allergens—such as insect venom, a drug, or certain foods. In sensitive individuals, being exposed to an allergen for the first time stimulates the body to produce antibodies to that allergen. These antibodies bind to special cells in the blood (basophils) and tissues (mast cells). When the individual is re-exposed to the allergen, those bound antibodies trigger the release of histamine and other chemicals that cause swelling and damage surrounding tissues.

    • Insects. Some sensitive people have an allergic reaction after getting stung or bitten by an insect. Bees, wasps, yellow jackets, hornets, or fire ants are common culprits.
    • Drugs. Certain drugs, vaccines, and dyes used for medical tests may trigger a reaction Table 01. Penicillin and similar antibiotics are the most frequent examples. Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDS—ibuprofen and others) are others. Some cancer patients are allergic to chemotherapy drugs, and certain people with diabetes cannot tolerate insulin injections. Others are hypersensitive to the dyes used for diagnostic tests, such as the contrast dye used in CT scans. Some people receiving treatment to prevent allergic reactions may even be allergic to these preventative drugs.
    • Food. Eating certain foods or food additives can cause allergic reactions Table 02. Peanuts, other nuts such as cashews and walnuts, and seeds are some common offenders. Some people are highly allergic to seafood—shellfish in particular. For others, eating certain types of fruit—such as apples, bananas, peaches, oranges, and melons—can trigger an allergic reaction. Dyes and other additives used in foods have been known to cause reactions as well.
    • Some people experience reactions in response to the heat or the cold. Vigorous exercise can result in breathing problems.

    Table 1.  Medications and Other Substances Linked to Allergic Reactions

    Antibiotics
    Cephalosporins
    Ciprofloxacin
    Nitrofurantoin
    Penicillin and derivatives
    Sulfonamides
    Tetracycline
    Vancomycin
    Chemotherapy drugs
    Asparaginase
    Cyclosporine
    5-Fluorouracil
    Methotrexate
    Vincristine
    Painkillers
    Aspirin (Bayer)
    Nonsteroidal anti-inflammatory drugs (NSAIDs)
    Opiates
    Other
    Allergy extracts?such as those you might receive during immunotherapy (allergy shots)
    Contrast dyes?used for diagnosing certain disorders
    Dextran
    Glucocorticoids
    Heparin
    Insulin
    Human gamma globulin
    Protamine
    Vaccines
    Latex?found in gloves and condoms

    Table 2.  Foods Linked to Allergic Reactions

    Chocolate
    Corn, cornmeal, or popcorn
    Eggs
    Fish
    Fruits (apples, bananas, peaches, oranges, melons)
    Legumes (beans, peanuts, peas, soybeans)
    Milk products
    Nuts (almonds, cashews, pecans, walnuts)
    Potato
    Seeds (cottonseed, poppy, sesame, sunflower)
    Spices (cinnamon, nutmeg, mustard, sage)

    Allergic reactions produce an array of symptoms that can affect the skin, lungs and airways, and the heart and cirulatory system—usually within an hour of exposure. Table 03 Reactions range in severity. Typically, the faster symptoms come on the worse the reaction will be. Skin symptoms such as flushing and itchiness are typical. Red, raised swellings with a white center (hives) are another allergic skin reaction. Allergic reactions can cause swelling in the airways, making it hard to breathe. The person may feel the throat closing in or tightening in the chest. Sometimes blood pressure drops quickly and causes weakness and fainting, or the heart starts beating erratically. This places the person in a state of extreme distress. He or she may feel nauseous and vomit.

    Table 3.  Symptoms of Allergic Reactions

    Skin flushing, redness, hives, itching
    Eye and Nose red, watery eyes; runny nose, congestion, sneezing
    Respiratory Throat swelling, chest tightness
    Cardiovascular Heartbeat abnormalities, severe drop in blood pressure, dizziness
    Gastrointestinal Abdominal pain, nausea and vomiting

    People who have a history of allergies are the most likely to have an allergic reaction. Allergic reactions from aspirin and latex occur more frequently in women, and those from insect stings occur more frequently in men. This seems to have more to do with exposure than gender. People who have heart disease or asthma tend to have more severe allergic reactions than others.

    To determine what is causing your symptoms, the doctor will conduct a medical history and do a physical examination. Allergic reactions are pretty obvious, as the symptoms usually come on shortly after exposure to the allergen. The physician treating you will check your blood pressure, pulse, and respiration, and ask you if you were exposed to any possible triggers (foods, medications, stings, etc.) prior to the reaction.

    The doctor may refer you to an allergist for skin tests. Skin tests involve injecting tiny amounts of various allergens (insect venoms, drugs, etc.) into your skin and waiting to see if a skin reaction occurs. If you are allergic to any of them, a hivelike swelling should form within 20 minutes.

    After you have received the emergency medical treatment necessary—a combination that could include epinephrine (adrenaline), an antihistamine or corticosteroids, or heart drugs to stop an abnormal heart rhythm—and are stable, your doctor may run diagnostic tests to determine what caused the reaction. The doctor may wish to check blood levels of antibodies to specific allergens with a test called the radioallergosorbent test (RAST). X-rays will be taken if you have breathing symptoms or chest pain.

    If a food is the suspected culprit, you may be asked to take tests to isolate the specific cause. Diagnosing food allergies sometimes requires detective work. After a positive skin test, your allergist may have you consume the suspected trigger food disguised in something (such as applesauce) and wait for a reaction. Your allergist may also wish to have you follow an elimination diet. For this test, you begin by cutting out all possible allergenic foods. Then, you start adding them back, one at a time, to see if a reaction occurs. As the name suggests, this diagnostic tool works by process of elimination.

    Alert your doctor to any known drug allergies you have and read package inserts before taking any medication. Steer clear of any drug to which you have a known allergy. In addition, stay away from drugs that are related to your known allergen, as related medications could cause a reaction as well. For example, if you are allergic to aspirin, do not take NSAIDs (ibuprofen, ketoprofen, naproxen, etc.); if you are allergic to penicillin, let your doctor know so he or she will not prescribe penicillin-related medications, such as amoxicillin. Always read package inserts for warnings just in case.

    Read food labels and look for ingredients that could trigger an allergic reaction. Take precautionary measures when preparing food and dining out. If you know you are allergic to shrimp, obviously you know to pass on the shrimp cocktail. However, be aware that shrimp may be hidden in salads, casseroles, and other dishes. Be sure to ask before you eat. Some people are so sensitive that the steam from shellfish being cooked can trigger a reaction. These people should avoid restaurants with open kitchens or hibachi-style cooking tables.

    Peanut allergies can be very severe and can occur at the slightest exposure. There have been reports of allergic reactions occurring in children who ate sandwiches that were cut with the same knife used to make peanut butter and jelly sandwiches for other kids. Be sure the cafeteria workers at your child’s school know of any allergies your child may have. Be sure to inform the parents of your child’s friends as well, to cut the risk that harmful food is served to your child unknowingly. When grocery shopping, read food labels carefully, checking for ingredients that may trigger reactions. Eggs may show up in ingredient lists as albumin, binders, or emulsifiers. The ingredients casein, lactose, and whey are derived from milk. When dining out, let the waiter or waitress know you have a food allergy and ask about the ingredients in the dish you are considering.

    If you are highly allergic to stings, you may want to consider a treatment known as allergen immunotherapy to desensitize yourself to the allergen. Latex desensitization is not available in the U.S. Food immunotherapy is not effective, and may be dangerous. For this therapy, a small amount of allergen is injected under the skin. The amount is too small to cause a reaction, but large enough to block or damp down any reaction that might occur with subsequent exposure to the allergen.

  • Prevention and Screening

    Alert your doctor to any known drug allergies you have and read package inserts before taking any medication. Steer clear of any drug to which you have a known allergy. In addition, stay away from drugs that are related to your known allergen, as related medications could cause a reaction as well. For example, if you are allergic to aspirin, do not take NSAIDs (ibuprofen, ketoprofen, naproxen, etc.); if you are allergic to penicillin, let your doctor know so he or she will not prescribe penicillin-related medications, such as amoxicillin. Always read package inserts for warnings just in case.

    Read food labels and look for ingredients that could trigger an allergic reaction. Take precautionary measures when preparing food and dining out. If you know you are allergic to shrimp, obviously you know to pass on the shrimp cocktail. However, be aware that shrimp may be hidden in salads, casseroles, and other dishes. Be sure to ask before you eat. Some people are so sensitive that the steam from shellfish being cooked can trigger a reaction. These people should avoid restaurants with open kitchens or hibachi-style cooking tables.

    Peanut allergies can be very severe and can occur at the slightest exposure. There have been reports of allergic reactions occurring in children who ate sandwiches that were cut with the same knife used to make peanut butter and jelly sandwiches for other kids. Be sure the cafeteria workers at your child’s school know of any allergies your child may have. Be sure to inform the parents of your child’s friends as well, to cut the risk that harmful food is served to your child unknowingly. When grocery shopping, read food labels carefully, checking for ingredients that may trigger reactions. Eggs may show up in ingredient lists as albumin, binders, or emulsifiers. The ingredients casein, lactose, and whey are derived from milk. When dining out, let the waiter or waitress know you have a food allergy and ask about the ingredients in the dish you are considering.

    If you are highly allergic to stings, you may want to consider a treatment known as allergen immunotherapy to desensitize yourself to the allergen. Latex desensitization is not available in the U.S. Food immunotherapy is not effective, and may be dangerous. For this therapy, a small amount of allergen is injected under the skin. The amount is too small to cause a reaction, but large enough to block or damp down any reaction that might occur with subsequent exposure to the allergen.

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