Allergic rhinitis (hay fever), asthma and atopic eczema are among the most common causes of chronic ill health. There is also clear evidence that in the Western world these disorders are increasing in frequency. The development of allergic disease relates to a complex interplay of genetic and environmental differences. Since no significant genetic changes have occurred in the last 2 decades, we must assume that environmental factors are most likely responsible for this trend. The reunification of Germany offered tremendous insight into the impact of environmental changes on allergic conditions. These disorders were less common in East Germany than in West Germany before reunification, where as since that geopolitical change occurred, the prevalence of allergic problems (except asthma) has increased among children who spent their early childhood in East Germany. This interesting observation raises the possibility that somehow the Western lifestyle accounts for this change. Perhaps this Western lifestyle deprives the developing immune system sufficient exposure to infectious agents, to nurture "allergy protective" infection-fighting immune responses. A relatively clean environment and the use of antibiotics for minor illnesses in early life may sway the immune system towards "allergy promoting" responses instead. This describes the so-called "Hygiene Theory", which attempts to explain the rising incidence of allergic diseases. Other examples, which illustrate this, include: Lower incidence of allergy in those living on farms (or rural areas) due to more exposure to bacteria in barns. Lower incidence of allergy in younger children of large families (3 or more older siblings) due to repeated exposure to infection from older siblings. Lower incidence of asthma and wheezing in children who go to day care centers, where they are exposed to more infections.

Pollen grains from trees, grasses and weeds can float through the air in spring, summer or fall. But along with staying on mission to fertilize plants and tree flowers, pollen particles often end up in our noses, eyes, ears and mouths. The result can be sneezing spells, watery eyes, congestion and an itchy throat. Pollen allergy, commonly known as hay fever, affects about 1 out of 10 Americans, according to the National Institute of Allergy and Infectious Diseases (NIAID). For some, symptoms can be controlled with occasional over-the-counter (OTC) medicine. Others have reactions that may more seriously disrupt the quality of their lives. Allergies can trigger or worsen asthma and lead to other health problems such as sinusitis and ear infections in children. You can distinguish allergy symptoms from a cold because a cold tends to be short-lived, results in thicker nasal secretions, and is usually associated with sore throat, hoarseness, malaise, and fever. Many people with seasonal allergic rhinitis notice a seasonal pattern with their symptoms, but others may need a doctor's help to find out for sure that pollen is the source of their misery. If these symptoms crop up year-round, dust mites, pet dander or another indoor allergen could be the culprit. This is known as perennial allergic rhinitis. Once you know you have seasonal allergies, probably the most important step you can take is to avoid pollen as much as possible. Try to stay indoors when pollen levels are highest. In the fall ragweed pollen season, pollen levels are highest in the morning. During the grass pollen season in the spring and summer, pollen levels are highest in the evening. Pollen counts measure how much pollen is in the air and are expressed in grains of pollen per square meter of air collected during a 24-hour period. It may also help to keep windows closed in your house and car and to run the air conditioner. If possible, avoid mowing grass and other yard work.

In 1819, an English physician, John Bostock, first described hay fever by detailing his own seasonal nasal symptoms, which he called "summer catarrh." The condition was called hay fever because it was thought to be caused by "new hay." Asthma - Asthma is a breathing problem that results from the inflammation and spasm of the lung's air passages (bronchial tubes). The inflammation causes a narrowing of the air passages, which limits the flow of air into and out of the lungs. Asthma is most often, but not always, related to allergies. Common symptoms include: Shortness of breath Wheezing Coughing Chest tightness Allergic Eyes. Allergic Eyes - (Allergic Conjunctivitis) is inflammation of the tissue layers (membranes) that cover the surface of the eyeball and the undersurface of the eyelid. The inflammation occurs a result of an allergic reaction and may produce the following symptoms: Redness under the lids and of the eye overall Watery, itchy eyes Swelling of the membranes. Allergic Eczema - Allergic Eczema (Atopic Dermatitis) is an allergic rash that is usually not caused by skin contact with an allergen. This condition is commonly associated with allergic rhinitis or asthma and features the following symptoms: Itching, redness, and or dryness of the skin Rash on the face, especially children Rash around the eyes, in the elbow creases, and behind the knees, especially in adults. Hives - Hives (Urticaria) are skin reactions that appear as itchy swellings and can occur on any part of the body. Hives can be caused by an allergic reaction, such as to a food or medication, but they also may occur in non-allergic people. Typical hive symptoms are: Raised red welts Intense itching Allergic Shock - Allergic Shock (Anaphylaxis or Anaphylactic Shock) is a life-threatening allergic reaction that can affect a number of organs at the same time. This response typically occurs when the allergen is eaten (for example, foods) or injected (for example, a bee sting). Some or all of the following symptoms may occur: Hives or reddish discoloration of the skin Nasal congestion Swelling of the throat Stomach pain, nausea, vomiting Shortness of breath, wheezing Low blood pressure or shock. Shock refers to the insufficient circulation of blood to the body's tissues. Shock is most commonly caused by blood loss or an infection. Allergic shock is caused by dilated and "leaky" blood vessels, which result in a drop in blood pressure.

An allergy refers to a misguided reaction by our immune system in response to bodily contact with certain foreign substances. It is misguided because these foreign substances are usually harmless and remain so to non- allergic people. Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mite, molds, danders, and foods. To understand the language of allergy it is important to remember that allergens are substances that are foreign to the body and can cause an allergic reaction in certain people. When an allergen comes in contact with the body, it causes the immune system to develop an allergic reaction in persons who are allergic to it. When you inappropriately react to allergens that are normally harmless to other people, you are having an allergic reaction and can be referred to as allergic or atopic. Therefore, people who are prone to allergies are said to be allergic or "atopic." Austrian pediatrician Clemens Pirquet (1874-1929) first used the term allergy. He referred to both immunity that was beneficial and to the harmful hypersensitivity as "allergy." The word allergy is derived from the Greek words "allos," meaning different or changed and "ergos," meaning work or action. Allergy roughly refers to an "altered reaction." The word allergy was first used in 1905 to describe the adverse reactions of children who were given repeated shots of horse serum to fight infection. The following year, the term allergy was proposed to explain this unexpected "changed reactivity."