Allergy
Allergies are the immune system’s incorrect response to a foreign substance. Exposure to what is normally a harmless substance, such as pollen, causes the immune system to react as if the substance is harmful. Substances that cause allergies are called allergens.
When you come into contact with an allergen, you may experience a number of allergic symptoms including itchy, watery nose and eyes; asthma symptoms such as wheezing and coughing; or hives.
What is an allergic reaction?
A hypersensitive response, or allergic "reaction," is the result of how three factors interact with the body:
1. The allergen — Allergens include pollen, mold, dust mites, certain foods, latex, animal dander, and others.
2. Mast cells — Although mast cells are found throughout the body, most reside in connective tissues such as those of the skin, tongue, the lining of the nose and intestinal tract, the lungs, and upper airways.
3. Immunoglobulin E (IgE) — IgE is an allergic antibody, a type of protein made by the immune system to recognize and fight specific body "invaders." IgE coats the surface of the mast cells in tissues.
The first time an allergy-prone person is exposed to an allergen (such as pollen), large amounts of the corresponding IgE antibodies (for example, pollen 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. The eosinophils add more inflammatory chemicals.
If the allergen is in the air, the allergic reaction will occur in the eyes, nose and lungs. If the allergen is ingested, the allergic reaction will occur in the mouth, stomach, and intestines. Sometimes enough inflammatory chemicals are released to cause a reaction throughout the body, such as hives, decreased blood pressure, shock, or loss of consciousness. This severe type of reaction is called anaphylaxis and may be life-threatening.
What are the symptoms of allergies?
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. Symptoms may include itchiness that spreads or difficulty breathing.
- A severe allergic reaction, known as anaphylaxis, is a rare, life-threatening emergency 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
Dust mites are 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 (ongoing). - Molds
Molds are parasitic, microscopic fungi (like 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
The 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.
- 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. - 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. - 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.
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.
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.
What is allergic rhinitis?
Nasal allergy symptoms and hay fever are referred to as "allergic rhinitis." Seasonal allergic rhinitis describes nasal allergies that change with the seasons due to pollen from plants (trees, grasses, or weeds). Seasonal symptoms arise during the pollinating seasons for particular plants. Because you can be allergic to more than one thing, your symptoms may get worse at different times throughout the year, or they may appear constant (perennial).
Does everyone get allergies?
No. Most allergies are inherited, which means they are passed on to children by their parents. People inherit a tendency to be allergic, although not to any specific allergen. If a child develops an allergy, it is very likely that at least one of his or her parents has allergies. Being exposed to allergens at certain times when the body’s defenses are low or weak, such as after a viral infection or during pregnancy, also may contribute to the development of allergies.
How common are allergies?
Allergic disorders affect more than 20 percent of adults and children (40 to 50 million people) and are the sixth leading cause of chronic illness in the United States, according to the Allergy Report from the American Academy of Allergy, Asthma and Immunology.
How are allergies diagnosed?
If you think you have allergies, don’t wait to see if your symptoms will go away. When your symptoms last longer than a week or two and tend to recur, make an appointment with your doctor so a complete medical evaluation can be performed.
An allergy skin test, also called a prick test, may be used to identify the substances that are causing your allergy symptoms. The test is performed by pricking your skin with an extract of an allergen, and then evaluating the skin’s reaction.
If a skin test cannot be performed, a radioallergosorbent blood test (RAST) may be taken, although its results are not as accurate as a skin test. This RAST evaluates the number of antibodies produced by the immune system. Elevated levels of certain antibodies can identify particular allergies.
How are allergies treated?
Medications such as antihistamines, decongestants, or a combination of both are available over-the-counter or by prescription to treat allergy symptoms. Nasal sprays such as topical nasal steroids and cromolyn sodium also can be used to treat allergy symptoms. Immunotherapy, or allergy shots, is recommended for relief that is needed over a long period of time.
Can allergies be prevented?
Allergies cannot be prevented, but they can be treated and controlled. Making changes in your environment can greatly limit your exposure to certain allergens and reduce your symptoms.