With so many potentially allergenic substances, it's no wonder allergic diseases are among the major causes of illness and disability in the United States. According to the American Academy of Allergy, Asthma & Immunology (AAAAI), the prevalence of allergies has continued to rise in industrialized countries for more than 50 years. Worldwide, up to 30 percent of people suffer from seasonal and year-round allergic rhinitis, and 20 percent suffer from skin allergies.
An allergy is a response of a person's immune system to a normally harmless substance, one that doesn't usually cause problems for most people. In the allergic woman, an offending substance can trigger an immune system response, which functions as the body's defense against invading agents such as parasites, to respond to a "false alarm." The immune system treats the allergen as an invader by generating large amounts of a certain type of antibody—a disease-fighting protein known as IgE—that attaches to specific body tissue and blood cells. The cells are then triggered to release powerful inflammatory chemicals such as histamine, cytokines and leukotrienes. These chemicals can act on tissues in various parts of the body, such as the respiratory system, and cause the symptoms of the allergic response.
Allergies can be more than just bothersome. Some allergens cause symptoms of asthma and rhinitis like sneezing, runny nose, stuffiness and watery, itchy or red eyes; skin irritations like itching and hives or eczema; or gastrointestinal distress. In some people, the allergic response can lead to anaphylaxis or anaphylactic shock—a sudden and sometimes deadly drop in blood pressure. Anaphylactic shock can also potentially stop the heart or lead to complete closure of air passages, causing death by suffocation.
Pollens, molds and fungi, dust or dust mites, animal proteins, medications, foods, latex and other substances can trigger acute or chronic symptoms. Food allergies, which are most likely to cause anaphylaxis, are most commonly caused by ingestion of peanuts, tree nuts, shellfish, fish, milk, eggs, wheat and soy.
Contact allergies are allergic reactions caused by a person's skin touching a substance. They are most often caused by nickel, rugs, fabric softeners, deodorants, cosmetics, perfumes, preservatives, dyes and foam insulation. Plants such as poison ivy, poison oak and sumac are also leading causes of contact dermatitis. There is a compound in these plants that can cause severe skin reactions in people who are sensitive to it—up to 85 percent of Americans. Such reactions usually occur two days after exposure and can persist for weeks unless proper treatment is obtained. Testing for these substances is readily available.
Allergies can have a genetic component. If only one parent has allergies, a child has about a 30 percent to 40 percent chance of developing allergies. If both parents have allergies, the odds are closer to 70 percent.
Adults usually do not lose their allergies, but children may outgrow them. In addition, while people are born with a genetic predisposition to allergies, sometimes they don't develop them until well into adulthood. Exactly why this occurs is unknown.
The most common allergic responses are upper and lower airway problems such as nasal congestion (stuffiness, sneezing, runny nose) and wheezing, along with itchy, watery eyes. If you suffer from allergies, you may have experienced one or many of these symptoms:
- sneezing in bursts or single sneezes
- congestion or stuffiness (nasal blockage)
- runny nose or postnasal drip
- itching of nose and throat, including the palate and often the ear canals
- dark circles or "shiners" under the eyes caused by decreased venous blood flow due to poor drainage from persistent nasal congestion
- a crease mark on the nose from rubbing it upward over time (the "bunny crease")
- watery eyes
- itching of the eyes
- dry eyes
- conjunctivitis, or an inflammation of the membrane that lines the eyelids, causing red-rimmed, swollen eyes and sometimes crusting of the eyelids
- wheezing, coughing, chest tightness from allergic asthma or shortness of breath from exertion
In addition to these symptoms, some food allergies may cause the following symptoms:
- itching in the mouth (lips, throat, tongue or palate)
- difficulty breathing or swallowing
- a drop in blood pressure leading to feeling faint and weak
- abdominal pain
- diarrhea or vomiting
- hives or skin itching
- eczema (more common in children)
The main symptom of a contact allergy is an itchy, persistent rash.
Some women develop reactions in response to environmental agents, such as cigarette smoke, paint fumes, plastics and perfumes; temperature and humidity changes; and strong smells. These are not true allergic reactions involving antibodies and the release of histamine or other chemicals. Similarly, food intolerances, such as an inability to digest milk products or gluten or sensitivity to monosodium glutamate (MSG), are not true food allergies but are intolerances
It's not uncommon for women with allergies to develop asthma. The symptoms of asthma include coughing, wheezing and shortness of breath due to a narrowing of the bronchial passages or airways and to excess mucus production and inflammation and respiratory muscle contractions. Similarly, extended periods of rhinitis can lead to chronic sinusitis.
If you suspect you have an allergy and it bothers you to the point you need to seek treatment, you can see a general health care provider or an allergy specialist. If you have cold-like symptoms that last for more than two weeks, you should seek proper diagnosis and treatment. These symptoms can lead to sinusitis, which may require more aggressive treatment. Your health care professional will discuss with you your medical history, your symptoms and possible triggers.
Helpful questions to sort out your symptoms include:
- Do allergies run in your family? If so, which relatives have them, and what are they allergic to?
- Do you develop recurring symptoms at certain times of the year or are symptoms present year-round or both?
- Does being around pets trigger symptoms in your eyes, nose or chest?
- Do eating certain foods cause symptoms to erupt or flare?
- How long do your symptoms last? Days? Weeks? Or longer?
- What seems to make symptoms worse? What makes them better?
- Have you tried any medications to alleviate your symptoms? Were they successful or not?
- Are you taking any over-the-counter or prescription medications? If so, which ones? (It's always helpful to take your medications with you to the appointment.)
- Do you use the medications as prescribed by your health care professional?
- Are you allergic to any medications?
Your health care professional should examine your nasal mucous membranes, as well as your eyes, ears, mouth and throat. Nasal membranes may appear swollen and pale or bluish. If you have a suspected food allergy, you may be asked to undergo skin testing. A food and symptom diary is another useful tool to determine less obvious food allergies.
Allergy specialists use skin tests to determine the specific allergens that may be responsible for your allergies. He or she will inject diluted extracts from allergens—particular foods, pollens, dust mites, etc.—under your skin or to a tiny scratch or puncture on your arm or back. With a positive reaction, a raised, reddened area with a surrounding flush will appear at the test site, indicating antibodies to that specific allergen are present in the skin. Prick tests are done first; an intradermal test may also be required.
Your health care professional might also do a blood test, which is not as sensitive for definitive diagnosis as a skin test. Using a sample of your blood, the test looks for levels of antibodies to particular allergens. This type of testing can be helpful for people who have skin conditions such as rashes, hives or dermatographia that make it difficult to do skin testing or who have an unusual history of reacting to allergens not available for testing.
If your health care professional suspects a food allergy, he or she may suggest an elimination diet, but only if your reactions are not severe. This technique involves not eating any of the suspected foods for a week or two to see if your symptoms go away. Then, you return the food to your diet over several days to see if the symptoms reappear. A procedure used to objectively diagnose food or medication allergy is the challenge test. During a challenge test, you take a very small amount of an allergen by inhaling it or taking it by mouth. It’s very important that challenge tests be supervised by an allergist or other physician with specialized training in allergies.
Another kind of challenge test is the double-blind food challenge. You ingest a dried (or otherwise modified) form of suspect food—usually in a capsule form––under clinical supervision to see if a reaction occurs. Neither you nor the health care professional knows which capsule contains the allergen. This test should not be used if your reactions are severe. It's rarely performed because of its high cost and is used more often to rule out a food allergy in cases in which your health care professional suspects the reactions are due to something else. These oral food challenges may be done if blood tests or skin tests were negative or not definitive in pinpointing a specific food reaction.
Reviewed by Dr. Bruce Prenner
Allergy Partners of San Diego