The Allergic Reaction
Pollen grains contain "allergenic" components that bind to allergic antibodies known as immune globulin E, or IgE. This antibody is bound to mast cells on and within mucous membranes of the eye, nose and throat and lungs. Within minutes of attachment of the "allergen" (pollen component) and IgE, a molecular signal is sent to the mast cell which triggers a sudden release of mast cell granules containing histamine, and other biochemicals called "mediators" of inflammation. Histamine then binds to specific histamine receptors on nearby blood vessels, nerve cells and mucous glands leading to the immediate effects associated with seasonal allergy; sneezing, itching, mucous secretion, swelling of the mucous membrane. The mediators of inflammation released with histamine act as cellular magnets, attracting additional mast cells and other immune cells including eosinophils into the mucous membrane, within hours of the pollen allergen and IgE interaction. This "inflammation" associated with allergy leads to persistent symptoms that may be noted for hours and even days after the initial allergic reaction. With frequent exposure, chronic allergy symptoms occur which often do not respond to antihistamine treatment. This allergic reaction and inflammation can occur in the bronchial airways leading to asthma which is associated with one or any combination of cough, chest tightness, wheezing or shortness of breath.
Allergic antibody or IgE is produced by the immune system of "atopic" individuals who have a genetic tendency towards allergy. Twenty to thirty percent of the population is atopic, suffering from some type of allergic disorder. Immune globulin E can be produced in such individuals only after exposure to an allergenic substance such as certain tree, grass and weed pollens. Therefore, the very first exposure to an allergen does not lead to allergic symptoms, but rather to a "silent" sensitization process and formation of IgE antibody .
With pollen allergy, exposures over about three pollen seasons may be needed before enough specific IgE antibody is formed for one to experience typical allergy symptoms. Therefore, a ragweed allergic person moving to Bellingham from the east coast may experience minimal symptoms for the first two to three years ( as there is no ragweed on the west coast) and then begin to develop significant allergy symptoms to local allergens such as alder and birch pollen.
Treatment of Pollen Allergy
Suffering from allergy symptoms is not necessary. There are very effective medications that can help improve the quality of life of allergy sufferers. Moderate to severe allergy symptoms can be very disruptive and interfere with job performance and enjoyment of the outdoors.
Reducing exposures where possible is helpful in reducing allergic symptoms. Wearing extra outer garments and a hat when working outdoors and shedding these before entering the house will reduce the load of pollen allergen carried indoors. Wearing glasses or goggles when working outdoors during high pollen days can decrease eye allergy symptoms. Filtering air entering the house, or using a HEPA filter indoors may reduce indoor pollen concentrations. Working and exercising outdoors may be better tolerated in the morning and late evening when area pollen counts may be lower than in mid day and afternoon. Pets can carry pollens into the home and should be restricted to certain areas of the house, or outdoors.
For individuals with mild allergy symptoms, an antihistamine may be effective in controlling allergy symptoms. Over the counter options include Claritin, Zyrtec and Allegra, or their generic options; loratadine, cetirizine, fexofenadine. Cetirizine (Zyrtec) is often taken at night due to sedation in some individuals. For those with moderate to severe symptoms, antihistamines usually are not effective when used alone. As indicated above, histamine associated with the immediate allergic reaction is only part of the problem. Inflammation is the more important target for therapy. Using an anti-inflammatory nasal spray is advised to reduce allergic inflammation and the build up of allergy cells (mast cells and eosinophils) that lead to significant and persistent symptoms. Examples include Flonase (Fluticasone), Nasonex, Veramyst, Omnaris, Nasocort. Along with this therapy, oral antihistamines are usually beneficial. In addition, nasal spray antihistamine medication is available which can work within minutes for nasal itching, sneezing. These include Patanase, Astepro, and Astelin. A new one, Dymista combines an anti-inflammatory medication, Fluticasone, with a topical antihistamine, Azelastine (Astelin). In addition, "dry" aerosol nasal sprays are available, including Qnasl, and Zetonna. For long term control of moderate to severe allergy symptoms, allergy shots are effective. These are provided on a regular basis for three to five years or longer, and work by shifting the immune system response away from the allergic pathway and towards the "normal" or non allergic immune response. The best time to start allergy medications, antihistamines for mild allergy, and combination antihistamine and anti-inflammatory nasal spray for moderate to severe allergy, is before the onset of symptoms. Mid February is a good time to start in Whatcom County for tree pollen allergy sufferers, and the first of May for grass pollen allergic persons. The peak of grass pollen allergy symptoms in our county usually occurs at the same time that the cottonwood fluffs are drifting through the air and collecting on the ground. Therefore, those with allergy to cottonwood this time of year are actually reacting to the invisible grass pollen, and not to the cottonwood seeds or fluffs. Cottonwood trees actually pollinate in the springtime, before the fluffs are noted.
"Improving quality of life through the art and science of
asthma and allergy care"
William H. Anderson MD
Barkley Medical Center 2075 Barkley Blvd. Ste.220 Bellingham WA