How do allergies develop : The immune system is the body's organized defense mechanism against foreign invaders, particularly infections. Its job is to recognize and react to these foreign substances, which are called antigens. Antigens are substances that are capable of causing the production of antibodies. Antigens may or may not lead to an allergic reaction. Allergens are certain antigens that cause an allergic reaction and the production of IgE. The aim of the immune system is to mobilize its forces at the site of invasion and destroy the enemy. One of the ways it does this is to create protective proteins called antibodies that are specifically targeted against particular foreign substances. These antibodies, or immunoglobulins are protective and help destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it. The allergic person however, develops a specific type of antibody called immunoglobulin in response to certain normally harmless foreign substances, such as cat dander. To summarize, immunoglobulins are a group of protein molecules that act as antibodies.

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.

Rhinitis is inflammation of the inner lining of the nose. Allergic rhinitis is characterized by an itchy/runny nose, sneezing, and nasal congestion. Other allergic symptoms include itchy ears and throat, Eustachian tube problems, red/watery eyes, cough, fatigue/loss of concentration/lack of energy from loss of sleep, and headaches or facial tenderness. Rhinitis can be either acute or chronic. Seasonal allergic rhinitis (also called hay fever) is usually caused by pollen in the air, and sensitive patients have symptoms during peak times during the year. Perennial allergic rhinitis, a type of chronic rhinitis is a year-around problem, and is often caused by indoor allergens, such as dust and animal dander. Symptoms tend to occur regardless of the time of the year. Non-allergic rhinitis (also called vasomotor rhinitis) occurs in those patients in whom an allergic cause cannot be identified. Vasomotor rhinitis is thought to occur because of abnormal regulation of nasal blood flow. Post-nasal drip is a 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. Chronic rhinitis is characterized by persistent irritation and inflammation of the lining tissues of the nose. One of the most common characteristics of chronic rhinitis is post- nasal drip. Post-nasal drip may lead to chronic sore throat. Post-nasal drip can be caused by excessive or thick secretions or an impairment in the normal clearance of mucus from the nose or throat.

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."