IgE is an antibody that all of us have in small amounts. Allergic persons, however, produce IgE in large quantities. Normally, this antibody is important in protecting us from parasites, but not allergens. During the sensitization period, IgE is being overproduced and coats certain potentially explosive cells that contain chemicals. These cells are capable of causing an allergic reaction on subsequent exposures to the dander. This is because the reaction of the cat dander with the dander IgE irritates the cells and leads to the release of various chemicals, including histamine. These chemicals, in turn, cause inflammation and the typical allergic symptoms. This is how the immune system becomes misguided and primed to cause an allergic reaction when stimulated by an allergen.

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.

Here's a rundown of drug options that can help you survive the sneezing season: Nasal corticosteroids: These are typically sprayed or inhaled into the nose once or twice a day. The newer drugs in this category are Nasonex (mometasone furoate) and Flonase (fluticasone propionate). Side effects may include stinging in the nose. Oral antihistamines: These drugs, which are available in both OTC and prescription forms, counteract the action of histamine, a substance released in the body during an allergic reaction. Benadryl (diphenhydramine) and Chlor-Trimeton (chlorpheniramine) are examples of OTC antihistamines. Drowsiness is a common side effect, so don't take the drug when you have to drive, operate machinery, or engage in other activities that require you to be alert. You could try newer and relatively non-sedating antihistamines that are available by prescription such as Clarinex (desloratadine), Claritin (loratadine), or Allegra (fexofenadine). Zyrtec (cetirizine), also available by prescription, has sedation frequency slightly higher than the relatively non-sedating antihistamines mentioned above. Last May, the FDA held a public hearing that discussed whether Claritin, Allegra and Zyrtec should be moved from prescription to OTC status. The FDA has not made a final decision yet. Decongestants: Decongestants are available both by prescription and over-the-counter. These drugs come in oral and nasal spray forms, and are sometimes recommended in combination with antihistamines. Antihistamines alone do not have an effect on nasal congestion. Allegra D (fexofenadine and pseudoephedrine) is an example of a prescription drug that contains both an antihistamine (fexofenadine) and a decongestant (pseudoephedrine). Note that prolonged use of nose sprays and drops can result in even worse nasal congestion. Non-steroidal nasal sprays: NasalCrom (cromolyn sodium) nasal spray which is available without a prescription, can help prevent symptoms of allergic rhinitis if used before symptoms start. It's a non-steroidal anti-inflammatory drug and needs to be used more often than the nasal steroids, three to four times a day.

Allergy Terminology : Acute Rhinitis - Inflammation of the nose that occurs for only a few days. Typically this is caused by a virus ("a cold"); if it goes on beyond a week then it is probably bacterial. Allergens - Normally harmless substances which cause an exaggerated allergic reaction (inflammatory response) in sensitive people. Allergic Rhinitis - Medical term for hay fever, a condition due to allergy that mimics a chronic cold. (Hay fever is a misnomer since hay is not a usual cause of this problem and there is no fever. Many substances cause the allergic symptoms in hay fever. Allergic rhinitis is the correct term for this allergic reaction. (Rhinitis means "irritation of the nose" and is a derivative of Rhino, meaning "nose.") Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, and tearing eyes. Post-nasal dripping of clear mucus frequently causes a cough. Loss of smell is common and loss of taste occurs occasionally. Nose bleeding may occur if the condition is severe. Eye itching, redness, and tearing frequently accompany the nasal symptoms. Chronic Rhinitis - inflammation of the nose that goes on for weeks to months which is different from "a cold", and may be caused by allergy, nasal irritants, structural, or physiological problems. Hay Fever - A seasonal allergy to airborne particles characterized by runny/itchy nose and eyes, sneezing, itchy throat, excess mucus, and nasal congestion. It is a misnomer because it is not caused by hay and it does not produce a fever. Non-Allergic Rhinitis - Inflammatory condition of the nose without an obvious allergy cause. Post Nasal Drip - Mucous accumulation in the back of the nose and throat leading to or giving the sensation of mucus dripping downward from the back of the nose. Summer Cold - Similar to hay fever. Also a misnomer because it is not caused by a virus. Vasomotor Rhinitis - Similar to non-allergic rhinitis, thought to be mediated by an abnormal neuronal control of the blood vessels supplying the nose.