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Definition

Like clockwork, the sneezing and sniffling hits you every spring. Or maybe it's every fall. But chances are it's not a cold. You have allergies. So what are allergies? They are exaggerated reactions of the immune system to substances that in most people don't cause problems. Symptoms may be caused by different exposures such as a certain chemical affecting the skin, dust or pollen particles affecting the respiratory system, or particular foods affecting the stomach and intestines.

As many as 40 million to 50 million Americans may have allergies, according to the American Academy of Allergy, Asthma and Immunology. Allergies affect more than 20 percent of the U.S. population and allergic diseases are the sixth leading cause of chronic disease in the United States. And at least 35 million have seasonal allergic rhinitis, also known as hay fever.

Common allergens are pollen, molds, dust mites, animal dander, certain foods and medications, and latex.

Allergic rhinitis (AR), or hay fever, happens when an allergen is inhaled through the mouth or nose. Sometimes symptoms are year-round, meaning it could be triggered by dust mites, cockroaches, animal dander, pollen or mold spores. AR is the most common allergy and is considered a risk in developing asthma. Nearly 80 percent of people with asthma also have AR. Sinusitis is a common disease often triggered by AR. The condition is an acute or chronic inflammation of the nasal sinuses, the hollow cavities around the eyes and behind the nose. More than 15 percent of the U.S. population has this condition.

Eczema (atopic dermatitis). Eczema often happens when the allergen such as animal dander touches the skin. For 80 percent of people with the condition, symptoms started in childhood. More than 50 percent of sufferers develop asthma.

Hives (uritcaria) are caused by allergens such as foods, dust mites, pollens and animals. Medications include penicillin, sulfa, anti-seizure drugs, phenobarbital and aspirin.

Contact dermatitis. When skin contacts certain substances, usually a chemical, this condition may happen. Reaction may take hours or days to develop, as with poison ivy.

Allergic conjunctivitis is the most common eye allergy, occurring when airborne allergens get into the eye, irritating thin membranes covering the eyelids and the exposed surface of the eyes. Allergic conjunctivitis is in two forms: seasonal and perennial. The seasonal version is much more common, and is related to exposure to grass, tree and weed pollens and molds. The perennial form lasts throughout the year and can be triggered by dust mites, feathers or animal dander.

Food allergies may have severe and possibly life-threatening reactions, although this is not true for all people with food allergies. The most common triggers are cow's milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts. Food allergies are more common in children and are increasing in prevalence. However, many children may outgrow certain allergies.

Anaphylaxis. Anaphylaxis is a rare, potentially fatal allergic reaction affecting many parts of the body at once. A trigger may be an insect sting, a food, such as nuts or shellfish, or medications. Usually the reaction is immediate and progresses within minutes. You must get to a hospital right away. About 150 to 200 people in the United States die each year from food-related anaphylaxis, the Food Allergy & Anaphylaxis Network reports.

Prognosis

Allergies do not have a cure, but they can be controlled effectively with good prevention, awareness of your triggers and knowing how to manage symptoms if they happen. If you cannot deal effectively with allergies on your own, a doctor can help.

Basic Information About Allergies

What is an allergy?

Having an allergy means that your body perceives a harmless substance (the allergen) as dangerous and is mounting an internal battle to take care of it. This hypersensitive process is called an allergic reaction.

What is an allergen?

An allergen is a substance that your body perceives as dangerous, but which a non-allergic person's body ignores. Common allergens are pollen, molds, dust mites, animal dander, certain foods and medications, and latex.

What is the difference between an allergen and an antigen?

An antigen is a substance, usually a protein that the body perceives as foreign, which sets in motion an immune response. This is the way the body fights disease. An allergen is a specific type of antigen, which sets in motion a hypersensitive, or allergic reaction. Other types of antigens are bacteria and viruses. The difference between an allergen and other antigens is that the allergen is harmless to most people, whereas other antigens are indeed harmful.

What are antibodies?

Antibodies are proteins created by your body to fight the battle against the invader (the allergen/antigen). The first time your body encounters the antigen, some antibodies are produced. With each additional exposure, more antibodies are produced. In the beginning, you may not feel any reaction. But, as more antibodies are produced, you start to experience some symptoms of an allergic reaction.

How are allergies and asthma related?

Allergies can trigger an asthma attack, in which you may experience a feeling of tightness in the chest, difficulty breathing and wheezing. Having good control over your allergies can limit both the frequency and severity of asthma attacks.

What is an allergic reaction?

An allergic reaction is the process your body goes through when it senses the presence of an allergen. The allergen may be ingested as food or medication, inhaled through the mouth or nose, or may come in contact with the skin. When the body senses the presence of an allergen, antibodies are produced. The antibodies attach to mast cells, which release a substance called histamine. Histamine's job is to narrow the bronchial tubes in the lungs, dilate blood vessels, and produce secretions, such as mucus. Histamine is the main substance responsible for the symptoms characteristic of an allergic reaction. Medications that inhibit the release of histamines are called antihistamines. An allergic reaction is a hypersensitive reaction to a substance to which most people do not react.

 

Are allergies dangerous?

Most allergies are not dangerous, although they can make life miserable! The exception is anaphylaxis, which is a life-threatening emergency requiring immediate medical attention.

Symptoms of a mild reaction

In a mild reaction, the allergy sufferer may experience localized symptoms: rash/hives, itchy or watery eyes, and some congestion. In a mild reaction, the symptoms do not spread to other parts of the body.

Symptoms of a moderate reaction

In a moderate reaction, symptoms become stronger and may start to spread throughout the body. Breathing may become affected, and any itchiness may spread from one part of the body to the rest of the body. A moderate reaction can signal the beginning of anaphylaxis.

Symptoms of a severe or anaphylactic reaction

Anaphylaxis is a rare, life-threatening emergency requiring immediate medical attention. In anaphylaxis, the body's response to the allergen is sudden and systemic (meaning, the whole body is involved). While any allergen can potentially lead to an anaphylactic reaction, certain foods, medications and insect stings are the most likely culprits.

Symptoms include:

• Mental confusion, dizziness (due to a drop in blood pressure)
• Swelling (especially of the face, tongue and throat), and
• Difficulty breathing.

The person's condition can deteriorate rapidly (within minutes), leading to shock and even death.

People at increased risk of anaphylaxis (who may have already had a moderate reaction to a bee sting, for example) may carry with them an emergency kit containing injectable epinephrine (also known as adrenaline), prescribed by their physician. The epinephrine helps to constrict blood vessels, raising blood pressure, reducing the risk of shock. While the individual still needs to seek emergency care, the injected epinephrine "buys some time," allowing about 15 minutes travel time to a hospital emergency department. Because the symptoms can progress so rapidly, a person suffering an anaphylactic reaction may need assistance administering the injection. If you think you could be at increased risk of anaphylaxis, speak to your doctor about prescribing such a kit. The injections also come in a "pen" form, where the needle is not visible. The "pen" is place against a large muscle, such as the thigh. When the trigger is pushed, the needle with the epinephrine is injected into the muscle. The needle then retracts back into the "pen." Discuss the need to wear a MedicAlert® bracelet with your physician.

Dyes used in diagnostic testing that can precipitate an allergic reaction

There are some diagnostic tests that use an iodine contrast medium. People allergic to seafood may react to an iodine solution that is placed on the skin (topical), or taken internally, as a contrast medium. If you need to undergo such diagnostic tests, and you have seafood allergies or have had a rash after topical application of iodine be sure to discuss this with your physician. You could be at risk for anaphylaxis. Anytime you undergo diagnostic testing with a contrast medium, someone should be monitoring your blood pressure, heart rate and respiratory rate. You should mention any itchiness, agitation, nausea or other symptoms experienced during the test.

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