As many as two out of five Americans believe that they have allergies to certain foods. In point of fact, however, fewer than 1% have true food allergies. A food allergy occurs when the body's immune system reacts to otherwise harmless substances in certain foods. This is different from a food intolerance, which does not involve the immune system. While most food allergies are mild, in some cases they can cause anaphylactic shock, a serious, sometimes life-threatening, reaction. Food allergies affect mostly young children. With the exception of peanut allergy, the majority of children outgrow their food sensitivities.
Signs and SymptomsMany people who think they have food allergies actually have food intolerances. Symptoms of a true food allergy usually involve the skin and intestines and generally begin just after eating and not longer than two hours following ingestion of the particular food. Common symptoms include:
- Hives, itching, or eczema
- Nausea and vomiting, stomach cramps, indigestion, or diarrhea
- Swelling of the eyelids, face, lips, tongue, throat or other parts of the body (called angioedema)
- Wheezing, nasal congestion, or trouble breathing
- Lightheadedness, dizziness, or fainting
- Swelling of the throat and difficulty swallowing
- Difficulty breathing
- Rapid pulse
- Dizziness, lightheadedness or loss of consciousness
- Blue color to the skin and nails
In most cases, allergies occur when an individual who has a genetic sensitivity to certain allergens is exposed to the substance. Foods frequently responsible for food allergies include:
- Shellfish (such as shrimp, crab, and lobster)
- Tree nuts (namely, walnuts, almonds, and pecans)
- Peanuts (which are legumes, not true nuts)
- Fruits (particularly strawberries, but also melons, pineapple, and other tropical fruits)
- Food additives (such as dyes, thickeners, and preservatives; monosodium glutamate [MSG] is a common food allergy in this category)
- Wheat and other gluten-containing grains
- Cows milk and other dairy products
- Corn products
- Family history of allergies increases your risk of having allergies, including food allergies. If both parents have food allergies, you have a 75% chance of having one yourself; one parent, 30% to 40% and if neither parent has allergies, then you have a 10% to 15% chance.
- Excessive exposure to a particular food—for example, in Japan where rice is a staple, rice is a common food allergen; in Scandinavia the common allergen is codfish; in India, chickpeas.
DiagnosisA comprehensive history will be taken to find out what symptoms you experience after eating and how soon after eating they occur. Your doctor will also want to know how often you have had the reaction and what type of medical treatment was needed. Even if your symptoms seem clearly related to a specific food, your doctor may still want to do some tests to be sure that you have a true food allergy and to verify the food or foods responsible for your allergic reaction.
The food causing the allergy can sometimes be identified by:
- Elimination and re-challenging diet (also called elimination and provocation diet) — suspected foods are eliminated from the diet one at a time until the symptoms disappear. If there is still a question about what may be causing the symptoms, then individual foods are reintroduced one at a time to see if an allergic reaction develops. (Note – this would not be done if the allergic reaction is considered dangerous or life threatening.) This method is not fullproof but may be used to narrow the list of suspected foods.
- Skin testing in which a diluted amount of the food allergen is placed under the skin; if allergic, a raised, red skin lesion will appear, generally within 15 to 20 minutes.
- Blood tests (RAST and ELISA), which look for antibodies against the particular food allergens.
Preventive CareAlthough there is no guarantee of success, guidelines from reputable health agencies suggest some steps parents can take to reduce their child's chances of having food and other allergies. If either or both parents have a personal or family history of allergy (for example, asthma, eczema, hay fever, perennial allergic rhinitis [allergy to animals, dust mites, or molds]) the following measures are recommended:
- Avoiding common allergenic foods, in particular peanuts and tree nuts, during pregnancy and the months of nursing—peanut protein, as well as components of cow's milk, eggs, and wheat, are secreted into breast milk
- Exclusive breastfeeding—give your baby only breast milk for the first 6 months of life; use hypoallergenic formulas to supplement breastfeeding if needed. Not all studies on this subject agree, however. In fact, the latest and largest study on the topic of breastfeeding and its relationship to allergies, particular asthma, suggests that breastfeeding in the early months of life can prevent allergies until your child is 2 years old. But, breastfeeding may lead to an increased risk of allergies once your child is older than 2 years.
- Delaying giving your infant solid food until 6 months of age
- Delaying giving your child common allergenic foods as follows: dairy until age 1 year; eggs until age 2 years; peanuts, nuts, and fish until 3 years. Delaying foods allows the child's gastrointestinal tract to mature.
- Once an allergy has developed, carefully avoid the offending food.
Treatment ApproachThe goals of treatment are reduction of symptoms and avoidance of future allergic reactions. Once the particular food allergy is identified, the best way to accomplish this is by not eating that food. Treatment at the time of a reaction varies with the severity and type of symptoms. Mild or localized symptoms may subside without treatment. Antihistamines (available either by prescription or over the counter) are usually recommended to relieve mild itching, swelling, rash, runny nose, or headache. Soothing skin creams may provide some relief of rashes. Severe allergic reactions (anaphylactic shock) can come on suddenly and accelerate quickly; in this case, you must go to the hospital by ambulance immediately. In some instances, survival may depend on an injection of epinephrine (adrenaline). Self-administration of epinephrine is routinely taught tofood allergy sufferers and can be life saving. Avoiding the offending food is the best way to prevent future allergic reactions.
- Avoid offending foods. Careful reading of all package ingredients (many foods are processed with peanuts, eggs, or milk products such as whey); calling ahead when eating out; and taking your own food with you on trips may be helpful.
- If you have a history of anaphylactic shock, you should keep a preloaded syringe of epinephrine with you. Your doctor will teach you and a close family member how to use it in case the need arises. Plus, you should wear a medical bracelet or necklace indicating your particular food allergies.
- Antihistamines — for mild itching, swelling, rash, runny nose, or headache; available both by prescription and over the counter in many cold, sinus, and allergy remedies. These include diphenhydramine, cetirizine, clemastine , chlorpheniramine, desloratadine, fexofenadine, hydroxyzine, and loratadine. Possible side effects include drowsiness, irritability, dry mouth, and heart palpitations.
- Skin creams — to soothe rashes
- Epinephrine injection — for anaphylactic shock. If you have a food allergy that causes such a serious reaction, your doctor will have you carry an injectable epinepherine pen and teach you, and those with whom you spend a lot of time, how to use it in case of emergency.
Nutrition and Dietary SupplementsAlthough it will be necessary to diligently avoid foods that provoke an allergic reaction, it need not restrict variety in your diet. Studies show that the vast majority of people are allergic to only one or two foods. However, you may be cautioned to be aware of the families of foods to which you are allergic. For example, if you are allergic to walnuts, you may also be allergic to pecans and almonds; an allergy to shrimp may also mean an allergy to crab.
L. acidophilus are bacteria that inhabit the intestines and vagina and protect against the entrance and proliferation of organisms that can cause disease. Some experts suggest that L. acidophilus may help to lower the risk of allergies, including food allergies.
Although scientific evidence is lacking, lipase (a digestive enzyme responsible for the breakdown of fat) has been used by trained clinicians to treat food allergies.
Although the information to date is limited, some experts believe that vitamin C may be helpful for allergic conditions such as food allergies. This application needs further study, but may be related to the ability of vitamin C to improve immune function.
HerbsHerbal medicines have not been specifically tested for food allergies. There are a wide variety of herbs, however, that a qualified herbal specialist might consider to help treat your food allergies and your symptoms based on his or her clinical experience. Examples of some herbs such an expert might select are listed below. Each of these herbs might be considered because of its ability to treat either allergies in general or stomach symptoms:
- Chamomile, German (Matricaria recutita)
- Dandelion (Taraxacum officinale)
- Evening Primrose (Oenothera biennis)
- Flaxseed (Linum usitatissimum)
- Peppermint (Mentha x piperita)
Women who have a food allergy or a partner with a food allergy may be able to reduce the risk of allergy in their child by avoiding common allergenic foods during pregnancy and nursing.
Prognosis and ComplicationsFood allergies may cause symptoms ranging from mild abdominal discomfort to life-threatening anaphylaxis. The avoidance of offending foods may be easy if the food is uncommon or easily identified. However, the successful avoidance of offending foods often requires strict reading of all package ingredients and detailed inquiries when eating away from home. Children may outgrow food allergies (particularly to milk or soy), but adults are unlikely to lose their allergies.
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