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.

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.

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.

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.