Q. What is a food allergy?
A. A food allergy occurs when a person with an inherited tendency to allergy fails to develop a normal tolerance to usually harmless proteins, such as those found in peanut or milk. Instead, that person’s immune system identifies this food as an allergen and begins to create antibodies – called Immunoglobulin E or IgE – to guard against it. These antibodies will attach themselves to cells in the body called mast cells.
When the person again eats the food he or she has developed an allergy to, the proteins from it, in turn, become attached to the IgE antibodies. This causes the mast cells to rupture, releasing histamine and other powerful chemicals into the body. It is these chemicals that cause the symptoms of allergy.
Q. What are the symptoms of food allergy?
A. Not everyone will get all symptoms, and the signs and severity of reactions will vary from person to person. They can also differ from one attack to the next in the same person. That said, symptoms include:
- Tingling in the mouth
- Swelling of the tongue and throat / feeling of throat tightness
- Itchy skin, hives or skin redness
- Abdominal cramps
- Vomiting or diarrhea
- Breathing difficulty, wheezing
- Faintness due to a sudden drop in blood pressure
- In a severe anaphylactic attack, the allergic person can lose consciousness and is at risk of death.
Q. What are the most common triggers of food allergies?
A. The vast majority of food allergy reactions are caused by proteins in these 9 foods:
- tree nuts (e.g. almonds, cashews, hazelnuts, pecans, walnuts)
- shellfish (shrimp, crab, lobster, mussels, clams)
Health Canada also lists the food additive sulphites as one of the most common causes of allergy, though it is not a food protein as such.
Q. What is anaphylaxis?
A. This is a serious allergic reaction to a food protein, stinging insect or medication. Such a reaction has many symptoms (from the “symptoms of food allergy” list above) and engages one or more of the body’s systems: the gastrointestinal tract, the respiratory tract, the skin and the cardiovascular system. Anaphylaxis usually involves difficulty breathing and can lead to a loss of consciousness or even death.
Such a severe reaction must always be treated as a medical emergency. It is essential that those with food allergies be aware of the risk of anaphylaxis and carry an epinephrine auto-injector (known by the brands EpiPen or Twinject). Leading allergists recommend that epinephrine be used early if a person known to be at risk of anaphylaxis appears to be reacting to a food; do not wait to see if symptoms worsen. [For more on epinephrine and anaphylaxis, go to Allergic Living Podcasts.]
“Because of the unpredictability of reactions, early symptoms should never be ignored, especially if the person has suffered an anaphylactic reaction in past,” notes the Consensus Statement issued in December 2005 by the Canadian Society of Allergy and Clinical Immunology (“Anaphylaxis in Schools & Other Settings”).
Q. Are some people at greater risk of anaphylaxis?
A. While no one who has food allergies should be complacent, most allergists suggest that the risk of anaphylaxis increases when: the allergic person is asthmatic, has eczema or has experienced previous serious reactions. Allergists say that, in particular, those with asthma should be considered in a higher risk category.
Q. Why does asthma increase the risk in an anaphylactic reaction?
A. Asthmatics are prone to severe breathing difficulties in an allergic reaction, which is why the CSACI Consensus Statement expresses concern about asthmatics who are also at risk of anaphylaxis, and stresses that they MUST keep their asthma controlled. The CSACI says: “In cases where an anaphylactic reaction is suspected, but there is uncertainty whether or not the person is experiencing an asthma attack, epinephrine should be used first (e.g. before a puffer). Ephinephrine can be used to treat life-threatening asthma attacks as well as anaphylactic reactions.” The CSACI advises carrying epinephrine auto-injectors as well as puffers/inhalers.
Q. What is asthma?
A. Asthma is a chronic inflammatory lung disorder. If asthma is not controlled and the asthmatic’s hyper-responsive airways are exposed to an inhaled allergen (such as cat dander) or an irritant (such as cigarette smoke), the lining of the airways become inflamed, and produce of an excess of mucous. In addition, the muscles surrounding the bronchial tubes will constrict. The inflammation, mucous and constriction significantly reduce the size of the passageway of the airways, making it difficult to breathe. The asthmatic will cough, feel tightness in the chest and perhaps wheeze.
Q. How is asthma related to allergies?
A. About 80 per cent of asthma is triggered by allergens such as dust mites, animal dander, cockroach waste, pollen or mould – so asthma is largely an allergic disease.
As with other allergies, the asthmatic’s immune system identifies a protein (for instance grass pollen) as an allergen and creates antibodies to guard against it. These antibodies attach themselves to mast cells in the body. When the person again inhales the microscopic pollen, it becomes attached to the antibodies. This will cause the mast cells to rupture, releasing histamine, which inflames the bronchial tubes and lungs in an immune system over-response.
Some people have non-allergic asthma, which is triggered by irritants including cigarette smoke, air pollution and chemical fumes. Irritants, however, may also spark attacks in those with allergic asthma that is not well controlled.
Q. What are the symptoms of asthma?
A. Not everyone will get all symptoms, and not every asthmatic will wheeze. The signs include:
- Chronic coughing
- Shortness of breath
- Tightness in the chest
- Shallow, rapid breathing
- Breathing difficulty at night, causing sleep disturbance
- In a severe attack, the person will find breathing very difficult; he may have trouble speaking or concentrating; and he may have a bluish tinge to the lips and face.
Q. How is asthma controlled?
A. There is no cure for asthma, but with proper treatment, symptoms can be controlled and the asthmatic can have a normal lifestyle. Treatment will be based upon the severity of the asthma, as well as other health considerations particular to a patient.
The symptoms of mild to moderate asthma, where symptoms are only present occasionally and rarely interfere in daily life, can often be eliminated by reducing exposure to triggers, and if only very occasional, by using quick-relief bronchodilators (e.g.: Ventolin, Atrovent, Berotec), as needed.
Any cases which have ongoing symptoms, even if mild, may require daily use of a controller medication, such as inhaled corticosteroids (Flovent, Pulmicort QVar), leukotriene receptor antagonists (Singulair, Accolate), long-acting bronchodilators (Oxeze, Serevent) or a combination product (Advair, Symbicort). Again, eliminating exposure to allergens and irritants is an element of controlling persistent asthma. Allergy immunotherapy (or “allergy shots”) are the only option to permanently change an individual’s allergic asthma response.
Q. What about insect allergies, which insects can cause reactions?
A. The major offenders are those in the hymenoptera family: bees, wasps, hornets, yellow jackets and fire ants (which are native to the southeastern United States).
Q. What should I do if I’m allergic and I get stung?
A. Remove the stinger by scraping it out with a fingernail or a credit card. Trying to squeeze it out could release more venom. If you’ve been prescribed an epinephrine auto-injector (EpiPen or Twinject), use it and either have someone take you to the hospital or call 911 for an ambulance.
Q. What is venom immunotherapy?
A. These are allergy shots to desensitize a venom-allergic person to their stinging insect allergens. Ask your allergist if you could be a candidate. While insect allergy is difficult to live with, the good news is that this form of immunotherapy has been effective in up to 98 per cent of those treated.
Q. Besides food proteins and stinging insects, what else causes anaphylaxis?
A. Drugs, such as pencillin, and natural rubber latex can also cause life-threatening allergic reactions. Some allergic people will also experience anaphylaxis if they exercise vigorously after eating a certain food. Exercise can also cause asthma attacks in some asthmatics.
Reviewing (food allergy basics) Dr. Susan Waserman, president of the Canadian Society of Allergy and Clinical Immunology; (asthma basics) Dr. Mark Greenwald, vice president of the Asthma Society of Canada. Additional sources: Anaphylaxis in Schools & Other Settings (2005, published by the CSACI), American Academy of Allergy Asthma & Immunology (www.aaaai.org).