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Allergies (Hypersensitivity)

Allergies also known as hypersensitivity, is a reaction of your immune system to something it finds irritating. Many people with allergies often are sensitive to more than one thing. Substances that often cause allergic reactions, (allergens), include pollen, dust mites, mold spores, pet dander, certain foods, insect stings and medications. 

Scientists think both genes and the environment have something to do with how people get allergies. In many cases, the immune system will fight germs as it is your body's defense system. In most allergic reactions, however, the immune system is responding to a false alarm.

Allergies can cause a runny nose, sneezing, itching, rashes, swelling or asthma. Although many people find allergies annoying, most allergies are not life threatening. However, a severe reaction called anaphylaxis is life-threatening.

Allergic symptoms are the result of three factors interacting with the body:

1. The allergen.
2. Mast cells - while many mast cells are found throughout the body, most reside in connective tissues (the skin, tongue, the lining of the nose and intestinal tract, the lungs, and upper airways).
3. Immunoglobulin E (IgE) - an antibody protein produced by the immune system to fight specific "invaders." IgE coats the surface of the mast cells in tissues.

When a person is first exposed to an allergen, large amounts of IgE antibodies are produced. The IgE antibodies cause the mast cells to release inflammatory chemicals that cause swelling of tissues, as well as histamine and several other chemicals that cause itching, engorgement of blood vessels, increased secretions, and bronchospasm (tightening of muscles that surround the airways). Some of these chemicals attract white blood cells known as eosinophils, which add additional inflammatory chemicals.

Allergens in the air cause the the allergic reaction tol occur in the eyes, nose and lungs. If the allergen is ingested, the allergic reaction occurs in the mouth, stomach, and intestines. Sometimes enough inflammatory chemicals are released to cause an anaphylaxis reaction throughout the body, such as hives, decreased blood pressure, shock, or loss of consciousness.

>Allergy symptoms can be categorized as mild, moderate, or severe (anaphylactic). Mild reactions include local symptoms (affecting a specific area of the body) such as a rash or hives; itchy, watery eyes; and some congestion. Mild reactions do not spread to other parts of the body.  Moderate reactions include symptoms that spread to other parts of the body and may include itchiness that spreads or difficulty breathing.  A severe allergic reaction is rare, and life-threatening in which the body’s response to the allergen is sudden and affects the whole body (systemic). Anaphylaxis may begin with severe itching of the eyes or face and within minutes progresses to more serious symptoms, including swelling (which could result in difficulty swallowing and breathing); abdominal pain; cramps; vomiting; diarrhea; hives; and angioedema (hives in the throat). Mental confusion or dizziness also may be symptoms, since anaphylaxis causes a quick drop in blood pressure.

People can be allergic to a wide variety of substances, the most common of which are pollen and dust mites. Airborne allergens include:

• Pollen - Allergic rhinitis, or hay fever, is the allergic response to pollen. It causes inflammation and swelling of the lining of the nose, as well as the protective tissue of the eyes (conjunctiva). Symptoms include sneezing, congestion, and itchy, watery eyes. Treatment options include over-the-counter and prescription antihistamines, nasal steroids, and nasal cromolyn. Other ways to help reduce symptoms include avoiding pollen exposure by staying indoors when pollen counts are high, and closing windows and using air conditioning. Immunotherapy, or allergy shots, also may be used to treat pollen allergies.
• Dust mites - microscopic organisms that live in dust and in the fibers of household objects not frequently laundered, such as pillows, mattresses, carpet, and upholstery. Dust mites especially love warm, humid areas. House dust is a mixture of potentially allergenic materials, including fibers from different fabrics, dander from animals, bacteria, mold or fungus spores, food particles, bits of plants, or other allergens. The symptoms of dust mite allergy are similar to those of pollen allergy, and also can produce symptoms of asthma such as wheezing and coughing. To help manage dust mite allergies, try using dust mite covers (airtight plastic/polyurethane covers) over pillows, mattresses, and box springs. Also, remove carpeting or vacuum frequently using a vacuum cleaner with high-efficiency filters. Treatment may include medications such as antihistamines or decongestants. Immunotherapy may be recommended for people whose symptoms are chronic.
• Molds - are parasitic, microscopic fungi (e.g., Penicillium), with spores that float in the air like pollen. Mold is a common trigger for allergies and can be found in damp areas, such as the basement or bathroom, as well as in the outdoor environment in grass, leaf piles, hay, mulch, or under mushrooms. In some people, symptoms of mold allergy may be brought on or made worse by eating certain foods, such as cheese processed with fungi. Mold spores peak during hot, humid weather.  Symptoms include sneezing; congestion; itchy, watery eyes; runny nose; and coughing. Treatment options include antihistamines, nasal steroid sprays, and immunotherapy.
• Animal dander - proteins secreted by oil glands in an animal’s skin, which are shed in dander, and the proteins present in an animal’s saliva cause allergic reactions in some people. Allergies to animals can take two or more years to develop, and symptoms may not subside until months after ending contact with the animal.
  Symptoms include sneezing, congestion, and itchy, watery eyes. Treatment involves avoiding exposure to the animals that cause your allergies. Medications such as antihistamines or decongestants may be helpful. Immunotherapy may be recommended if you have severe symptoms from intermittent exposure.

Other allergens include:

• Latex - A latex allergy develops after some sensitizing contact with latex. Rubber gloves are the main source of allergic reactions. A component of the latex substance itself is an allergen for many people. The latex glove powder residue is an airborne allergen that causes upper airway allergic reactions in some people, as well as worsening asthma.  Skin rash, hives, eye tearing and irritation, wheezing, and itching of the skin are common symptoms of latex allergy. Allergic reactions to latex can range from skin redness and itching to much more serious symptoms. A more severe reaction can occur if there is extensive exposure of the mucosal membrane, such as during an operation or gynecologic exam.
  
  Treatment of latex reactions begins by removing the offending latex product. Drug treatment also may be used, according to the type of symptoms developing. If you have latex allergy, it is important for you to wear a Medic Alert bracelet and carry an emergency epinephrine kit. There is no cure for latex allergy, so the best treatment for this condition is prevention.
• Certain foods
  Food allergies develop when there is an IgE antibody to a specific food. An allergic reaction occurs within minutes of eating the food, and symptoms can be severe. Shellfish, peanuts, and tree nuts are the most common food allergies in adults. Milk, eggs, soy, wheat, shellfish, peanuts, and tree nuts are the most common food allergies in children. Non-allergic food intolerance is more common than true food allergy.  Symptoms of food allergy include asthma (wheezing, coughing), hives, runny nose, vomiting, diarrhea, and swelling in the area around the mouth. The best treatment is to avoid the foods that cause allergy symptoms. For rashes, skin creams may ease discomfort, while antihistamines will help reduce itching, congestion, and other symptoms. For more serious reactions, corticosteroids such as prednisone will help to reverse severe generalized symptoms. In life-threatening situations, an epinephrine (adrenaline) injection immediately begins reversing symptoms and is the only effective treatment option.
• Insect venom (stings)
  If stung by a bee, the bee usually leaves a sac of venom and a stinger in the victim's skin. If the sac is still in the skin, gently scrape it out with a fingernail or a stiff-edged object like a credit card. Do not pull on the stinger, as this will cause the release of more venom into the skin.  A normal reaction will result in pain, swelling, and redness around the sting site. A large, local reaction will result in swelling that extends beyond the sting site. For example, a person stung on the ankle may have swelling of the entire leg. The most serious reaction to an insect sting is an allergic one, requiring immediate medical attention. Symptoms of an allergic reaction to an insect sting include difficulty breathing; hives that appear as a red, itchy rash that spreads to areas other than the immediate area stung; swelling of the face, throat, or mouth tissue; wheezing or difficulty swallowing; restlessness and anxiety; rapid pulse; and dizziness or a sharp drop in blood pressure.
  
  Take an oral antihistamine, such as Benadryl, to reduce itching, local swelling, and hives. To relieve pain, take aspirin or an aspirin-substitute. An allergic reaction is treated with epinephrine (adrenaline), either self-injected or administered by a doctor. Usually, this injection will stop the development of severe allergic reaction.