About 25 percent of people suffer from some sort of allergy. These allergies can manifest in a variety of ways, from mild skin eruptions to nasal congestion, and even severe respiratory distress. Regardless of the symptoms they cause, or the material (allergen) that initiates the allergic reaction, all allergies have something in common – namely, they are an immune system response to a substance that typically causes no reaction in the majority of the population. Common allergens include pollens, dust mites, various foods, animal dander and molds, although almost anything can induce an allergic reaction in susceptible people. It is important to note that not all reactions to specific substances are allergic. Some substances are simply toxic and the reaction they cause is direct and not mediated by an immune system reaction.
While the actual mechanism of allergic reactions is quite complicated, let’s try to simplify it to aid in our understanding of why allergic reactions occur and what we can do to minimize their effect on us.
The first step in the allergy chain is sensitization. In this step, one is exposed to an allergen, let’s say pollen. The pollen causes specific cells of the immune system to produce antibodies specific for that pollen. These antibodies are proteins called immunoglobulins, and will react only with the specific allergen that induced them. Unlike most antibodies, the immunoglobulins involved in allergic reactions, called IgE, do not circulate in the bloodstream, but rather bind to cells called mast cells that are present in the body’s connective tissues. On a subsequent exposure to the allergen, the antibodies on the mast cells interact with the allergen and results in the release of several chemicals from the mast cell, including histamine, which causes small blood vessels to dilate and makes smooth muscles in the trachea to tighten, heparin that decreases blood clotting and serotonin which causes larger blood vessels to contract. There are other chemicals released as well, but you get the basic idea. It is these chemicals that cause the symptoms that accompany an allergic reaction such as nasal stuffiness, trouble breathing, skin rashes and, in some cases vascular collapse (anaphylaxis), which can be fatal.
Why some people’s immune systems overreact to the presence of generally innocuous allergens while other’s do not is poorly understood. There may be a genetic component to this excessive sensitivity as allergies seem to run in families.
From a pilot’s perspective, typical allergies are a nuisance but are not serious. Nasal allergies however, can cause enough nasal congestion to result in blockage of the Eustachian tube (the tube that connects the middle ear to the nasopharynx) and this can result in severe pain with pressure changes, such as those occurring during climbs and descents. Pilots should therefore be cautious about flying if they are significantly congested. Those who are highly sensitive to specific allergens – like experiencing a vascular collapse after a bee sting – clearly need to do everything they can to avoid sharing the cockpit with a stinging insect. Additionally, they should carry an emergency kit with them for use should such a reaction occur.
The FAA does not consider allergies to be disqualifying per se, but does state that severe allergies require an FAA decision. How they define a “severe” allergy is uncertain.
Where the FAA is concerned about allergies is with the self-treatment of allergies by airmen. Because most of the symptoms experienced by allergy sufferers result from the action of the histamine released in the allergic reaction, treatment revolves around the use of anti-histamine medications, many of which are available over the counter (OTC).
It is imperative that pilots avoid the use of “first generation” antihistamines such as Benadryl (diphenhydramine), brompheniramine, chlorpheniramine, and doxylamine. These drugs are highly sedating and are found in a large variety of OTC preparations including popular anti-allergy medications such as Dimetapp, Chlortrimeton, NyQuil, and Alka Seltzer + Cold medicine. Read the label of any allergy medication you buy very carefully and do not use one containing the drugs mentioned above.
Newer, second generation antihistamines have the FAA’s blessing. They include Claritin, Alavert, Clarinex, Mucinex and Allegra. The FAA suggests that before flying with one of these medications, you use it a few times and make sure you suffer no side effects.
Of course the best advice is, as always, to use common sense. If you are having significant problems with allergies, don’t fly unless and until you can safely and reliably control your symptoms.
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