In the middle of the night in Atlanta, I got a frantic call from my daughter in Chicago. "Daddy, I'm so sorry to wake you, but Michael just ate a little piece of cashew and now his face is swollen and he's breaking out in a rash all over his body." Once I realized that her voice wasn't just part of some bad dream, I gave my doctor's orders: "Give him Benadryl and take him to the emergency room immediately!"
As a board-certified allergist for 25 years, I recognized that my grandson was having a potentially serious allergic reaction and that his symptoms could get worse-much worse. Fortunately, by the time they arrived at the hospital, the swelling had subsided and his hives had resolved.
Even though my grandson's diagnosis was easy to make, food allergies can be one of the most frustrating and complex allergy issues facing physicians, patients, and families. If you consider the unlimited number of foods and additives we consume today, the variable time between ingestion and allergic reaction, and the varied and often-subtle symptoms, it seems miraculous when an allergy-triggering food is actually identified.
Food Allergies In Children: A Disturbing Trend
Ask anyone who raised children 25 years ago if they ever heard of food allergies back then, and the likely answer will be no. Yet today, who doesn't know a child-if not several kids-who have severe food allergies? Pediatricians and allergists are observing first-hand that food allergies in infants and children have increased to epidemic proportions over the last few decades. Studies have shown that in the under-18 age group, the prevalence of reported food allergies increased 18% between 1997 and 2007. Approximately 4% of Americans are estimated to have food allergies. That's more than 12 million individuals. The prevalence of food allergies is even higher-6% to 8%-in infants and young children under three years old.
Any type of food can trigger an outbreak, yet the "Big 8" account for more than 90% of all cases: milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat. Sesame is quickly becoming another common cause of allergies, especially in those with Mediterranean diets. The good news is that the incidence of documented food allergies decreases with age, probably due to the development of tolerance in children allergic to milk, wheat, soy, and eggs. Of the 2.5% of children allergic to milk, approximately 80% will "outgrow" their allergy by age five. Kids with peanut or tree nut allergies aren't as lucky: Recent studies have shown that only about 10% to 20% of children will lose their allergy as they age.
Pediatric Food Allergies: Instantaneous Outbreak Of the two main types of allergies, the "immediate hypersensitivity reaction" gets the most hype, probably because you can see the symptoms (whether it's hives or swelling) right away. The other kind is aptly named "delayed hypersensitivity reaction." Otherwise known as IgE-mediated, the immediate allergic reaction is the best understood and the most easily diagnosed. Yet it can also be the most serious. When the proteins in an allergenic food come in contact with an IgE antibody (located in the skin, gut, and airways, or in the blood), a cascade of cellular events occurs resulting in the release of histamine and a multitude of other chemical mediators. The rapid release of the histamine and other chemicals is what causes the allergic reaction. The outbreak, which generally occurs within minutes of ingestion, can be relatively mild or severe. Moderate symptoms might include a rash, generalized itching and redness of the skin, facial or eyelid swelling, abdominal cramping, vomiting and/or diarrhea. These can be treated with a quick-acting antihistamine and tend to run their course over a few minutes to hours. The most severe reaction is called anaphylaxis, which can occur instantaneously or a few minutes after ingestion. As a general rule, the quicker the onset of symptoms, the more serious the reaction is likely to be. Symptoms of anaphylaxis might include those mentioned above, but can also rapidly progress to breathing difficulties and chest tightness (due to bronchial constriction and swelling of the airways), a drop in blood pressure leading to shock-and even death. Epinephrine (also known as adrenalin), which is available for self-injection in the form of an Epipen and other auto-injectors, must be given immediately and repeated if necessary. Foods that commonly cause severe reactions include peanuts, tree nuts, fish, sesame seeds, milk, and eggs. The most serious reaction I ever witnessed resulted from the ingestion of a single pine nut. That tiny seed (it's not really a nut) transformed a healthy teenager into a critically ill patient within a matter of minutes. Fortunately, the patient recovered, but anaphylaxis can be fatal if not treated immediately and aggressively. If your child has ever had an immediate allergic reaction to a food, you should consult with a board-certified allergist. To identify or confirm the symptom-triggering food, the allergist will likely give a few tests, either through the skin or blood. From there, you and your allergist can come up with a plan to eliminate the food from your child's diet and discuss prevention and management of future reactions.
Delayed Allergic Reactions: Subtle Yet Elusive
While less dangerous in terms of one's immediate health, the "delayed allergic reaction" can be much more difficult to diagnose and treat. As the name implies, it can take hours or even days after ingestion for the symptoms to show up, making it harder to establish a cause-and- effect relationship. The typical symptoms can involve several organ systems and may be quite subtle in their presentation. In addition to the classic allergy symptoms (think nasal congestion, a runny nose, and a rash), delayed reactions may also present with very vague and nonspecific symptoms, such as frequent headaches, recurrent or chronic abdominal pain, fatigue and lethargy, irritability, dark circles under the eyes, leg pains, and recurrent ear or sinus infections.
Part of the difficulty in diagnosing these food reactions is that there's no reliable allergy test that can accurately identify or predict a delayed outbreak. Skin testing and blood tests aren't helpful because they only measure the IgE antibody, which is responsible for immediate reactions. Research has not yet identified the antibody or antibodies responsible for delayed reactions, although there has been considerable interest and research in the possible role of the IgG antibody. Blood tests to measure this antibody are available, but its reliability as a predictor of delayed allergy has not yet been established.
So how can you figure out if your child's symptoms are the result of something he or she is eating? The best method we have right now is to eliminate the suspected food (or drink) from your kid's diet for four weeks. If you notice a significant improvement in symptoms, you're ready for the challenge phase: Serve the food in question for several days straight. If the symptoms start recurring, you can be relatively sure that a cause-and-effect relationship has been established. Even after avoiding the food culprit, it can still take a few weeks for symptoms to completely disappear, so be patient.
By far, milk and other dairy products are the most common cause of this type of reaction. Over the years, many teenagers have walked into my office with their parents complaining about stomach discomfort and profound tiredness. By the time they've come to see me, they've usually been through various tests and have seen multiple physicians, including gastroenterologists, and have often been diagnosed with irritable bowel syndrome. After hearing about their saga and symptoms-and seeing the dark circles under their eyes and their pale, sallow complexion-I can usually tell that it's a dairy allergy. Fortunately, many responded dramatically to a few weeks off of milk. They couldn't believe that the innocent act of drinking milk and eating dairy products could make them feel so ill-and that avoiding these products could restore their good health and vitality in such a short time.
Food Allergy Cross-Reactivity
If you're like me, you may have a food allergy that's directly connected to your sensitivity to tree and weed pollens. Called "oral allergy syndrome," this condition shows up when there's a cross-reactivity between tree or weed pollens and corresponding foods that share a common allergen. For example, because ragweed pollen and foods in the gourd family share a common allergen, people allergic to ragweed may exhibit symptoms after ingesting foods such as melons (watermelon, cantaloupe, and honeydew), zucchini, cucumber, and bananas. Because I'm allergic to ragweed pollen, I cannot eat melons or ripe bananas without developing intense itching in my throat. If you're sensitive to birch tree pollen, you may react to apples, pears, and apricots. Celery may be a problem for those allergic to mugwort pollen.
The typical symptoms, which are generally mild and transitory, are itching of the throat, mouth, and tongue. That aggravating throat itch often compels sufferers to rub their tongue against the soft palate, making a characteristic "clucking" sound. The vast majority of patients experience symptoms within five minutes of ingestion. Depending on the time of year, the presentation can be affected by the particular pollen season. The upside of this condition, which is the most common food-related allergy in adults, is that symptoms are only caused by the ingestion of raw or uncooked fruits or vegetables. The heating process that occurs during cooking breaks down the allergic protein, so you can eat boiled, baked, fried, or roasted fruits and veggies without triggering symptoms.
Allergies In Infants
Because of their age, newborns and infants can be especially sensitive to food allergies. Symptoms may include colic, irritability, excessive spitting and vomiting, rashes (including eczema or hives), nasal symptoms (such as congestion and runny nose), coughing or wheezing, and other gastrointestinal symptoms (diarrhea, bloody stools, or constipation). There can also be poor weight gain. Allergies in infants up to age one are almost always caused by food-most commonly cow's milk. Yet a baby doesn't have to drink milk straight for symptoms to break out: The proteins in cow's milk can enter the baby's system through some commercial formulas, as well as by passing through the mother's milk during nursing. A small percentage of milk-allergic babies are also allergic to soy.
In recent years, researchers have devoted themselves to understanding the disturbing rise of food allergies, especially in infants and kids. What they have discovered is leading allergists and physicians to dramatically revise recommendations on how and when we introduce foods to infants. For many decades, the time-honored and well-established approach was to delay the introduction of highly allergenic foods into the infant's diet to prevent the emergence of food allergies. For example, solid foods are generally not recommended until six months of age, cow's milk until one year, eggs until two years, and peanuts, tree nuts, and fish until three years. There is also a widely accepted notion that breast feeding alone for the first six months of life will minimize or delay the onset of food allergies and other allergic diseases (including asthma), as well as atopic dermatitis or eczema.
The latest medical evidence, however, is debunking these age-old theories. Indeed, the recommendation to delay the introduction of foods to infants as a means of preventing food allergies may be the wrong approach altogether. Recent studies have revealed very credible scientific evidence to suggest that the common practice of delaying the introduction of cow's milk, eggs, peanuts, and other foods may increase the child's risk of developing food allergies. And, even more importantly, there is evidence to suggest that the early introduction of allergenic foods may actually prevent the development of the allergy to that food. As an example, a recent study demonstrated that children in England were ten times more likely to be allergic to peanuts than children in Israel. One very strong hypothesis to explain this finding is the fact that Israeli infants are introduced to peanuts, generally through Bamba (a Peanut flavored snack that is used as a teething food), at about six months of age. On the other hand, children in England are generally not introduced to peanuts in any form until approximately three years of age. This study is just one of many that strongly suggest that an early introduction to certain foods can help babies build desensitization, thereby decreasing the risk of developing a food allergy.
Managing Severe Allergies
Historically, the treatment of serious food allergies has consisted of avoiding exposure and ingestion of the allergenic food, and making antihistamines and epinephrine immediately available. Total abstinence is indeed difficult and often impossible, as evidenced by the large number of accidental ingestions and allergic reactions that have resulted in emergency room visits. Even with strict avoidance measures, the potential for sudden and life-threatening outbreaks can lead to extreme anxiety in both the child-and the parent.
Fortunately, medical research has now proven that orally-administered immunotherapy can result in a significant degree of desensitization, or tolerance, to a given food in most allergic patients. This form of therapy, however, is associated with a significant amount of risk and should only be performed under the watchful eye of a board-certified allergist experienced in oral tolerance induction. Presently in the United States, this form of desensitization is being performed at a few highly-acclaimed medical centers.
An Allergy-Free Future
With all the time and money being put into food allergy research, there is excitement in the medical field about the possibility of new breakthroughs in the near future-both in prevention and treatment. I, for one, am optimistic that a safe and effective treatment is close at hand.
