Preventing Food Allergy

Food allergies are not the most predictable of illnesses. In some families, one child becomes allergic to peanut on his first exposure to it, while a half dozen of his siblings can chow down on peanuts without the slightest hint of a reaction.

A milk allergy becomes a lifelong companion to some, while other kids suffer through a few milk-sensitive years and then can chug a carton of milk without incident. Doctors and researchers can’t reliably predict the onset of food allergy or the course it will eventually take.

But we can provide some advice on possible strategies for preventing its onset and perhaps hastening its departure. The dramatic increase in the prevalence of food allergies over the past 20 years or so proves that the medical community hasn’t exactly made great strides in the prevention department.

But we’re hard at work trying to figure out why food allergies are on the rise and what we can do to prevent the onset of these allergies. Families that have a history of allergies may be able to improve the chances that their children. Especially their youngest children, can avoid the onset of food allergy and perhaps other allergic conditions, including asthma, by following the recommendations offered here.

The only two prevention strategies I recommend unconditionally are breastfeeding (over bottle feeding) and the avoidance of tobacco smoke. These two strategies can’t guarantee that your child will successfully dodge the food allergy bullet, but they can improve the odds.

Food allergies typically arise in the first two years of a child’s life, so prevention strategies focus on these critical years. For high-risk families (families with a history of allergic conditions, including asthma and allergic rhinitis), many doctors recommend avoiding highly allergenic foods, including milk, egg, and peanut, in the first two years of an infant’s life.

Sometimes, doctors also recommend that breastfeeding mothers avoid eating high-risk foods over the duration of the breastfeeding years. No studies have proven conclusively that strict avoidance is effective in preventing the onset of food allergies. In fact, a certain amount of exposure at the right time may be beneficial.

But since we don’t know how much exposure at what age is optimum, and because the ideal amount of exposure and the ideal age may vary from one person to another, we generally recommend that high-risk families avoid high-risk foods during the critical ages — up to three years of age.

Baby Formulas

Because food allergy is more prevalent in developed countries, especially in children, we asked ourselves, “What’s different about the way we raise children in developed countries?” One difference that immediately pops up on the radar screen is that instead of breastfeeding their children, parents in developed countries rely more heavily on baby formula, most of which is manufactured from — you guessed it — cow’s milk.

Tiffani Hayes, a pediatric nutritionist, and I published an article in September of 2005, in which we reviewed the data from several studies on baby formulas. What we discovered is that alternatives to cow’s milk formulas — including extensively hydrolyzed casein formulas and partially hydrolyzed whey formulas — are appropriate alternatives to breast milk for allergy prevention in infants at risk.

Because nobody can predict the onset of any allergy-related disease in any family, parents who cannot or choose not to breastfeed should consider the use of extensively hydrolyzed casein formulas and partially hydrolyzed whey formulas — hypoallergenic baby formulas.

This becomes even more important for families who have other children with allergic diseases such as atopic dermatitis (eczema), food allergy, asthma, and allergic rhinitis. Consult your doctor prior to giving birth to discuss the pros and cons of breastfeeding and different types of baby formulas.

Clearing the Smoke

One of the few factors that have been proven without a doubt to contribute to the onset of all types of allergies and asthma is cigarette smoke. If any of the thousands of other good reasons to quit smoking can’t convinces someone to give up smoking for good, perhaps the fact that cigarette smoke has been proven to increase a child’s vulnerability to allergic conditions will be sufficient.

Preventing Asthma

Parents in families that have a strong history of food allergy and asthma are often highly motivated to do whatever it takes to prevent the onset of food allergies and asthma in all their children. The problem with giving strict recommendations, however, is that we currently have very little conclusive proof on preventive strategies that work.

Recommending questionable prevention strategies can lead to other problems, such as malnutrition, or simply waste your time and money on something that’s not effective. My recommendation is to study the evidence for yourself, discuss the options with your doctor, keep up on the latest breakthroughs in food allergy research, and make the choices that you think are best for your child.

The most effective strategies are listed first followed by more questionable options:

  • Avoid tobacco smoke. Tobacco smoke is proven to contribute to the onset of all allergy-related conditions. Avoiding exposure to tobacco smoke, especially in the early years of life, can help stave off asthma, food allergies, and other allergy-related conditions.
  • Breastfeed exclusively. If possible, avoid baby formula for at least the first six months of your infant’s life. If you must use formula, choose a hypo-allergenic formula. Although breastfeeding has not been conclusively proven to prevent food allergies, it is far safer than cow’s milk and has so many other health benefits that doctors don’t hesitate to recommend it.
  • Use hypo-allergenic baby formulas. This is a good idea for all families who cannot or choose not to breastfeed or as a supplement to breastfeeding.
  • Restrict your diet while pregnant or breastfeeding. Some studies show that this is effective, and some don’t. I recommend that all mothers consider avoiding peanut and tree nuts during the last trimester of pregnancy and while breast feeding, especially mothers in high-risk families. I do not routinely recommend restricting other common allergens, such as milk and egg, since the evidence is not strong enough to justify putting the mother or baby at nutritional risk
  • Introduce probiotics. Probiotics are beneficial bacteria, such as those in yogurt. Some evidence shows that probiotics may help in preventing the onset of food allergies.
  • Waiting to introduce solid foods in the baby’s diet. Some studies have shown this to be effective, and others have not. I recommend that babies in high-risk families not be started on solids until 6 months of age.

Ranking Food by Food

A majority of children, even those with the most severe food allergies, often simply outgrow their allergy. When this occurs, what exactly happened to make the person less sensitive to the problem food? We don’t know for sure. All we know is that sometimes the body makes a few internal adjustments and the immune system stops overreacting to a particular food.

What are your or your child’s chances of outgrowing a food allergy? I can’t say for sure on a case-by-case basis. Some food allergies are easier to outgrow, and some people’s bodies seem better equipped than others to outgrow a food allergy.

I can, however, reveal some factors that may increase your chances of outgrowing a food allergy, such as the type of food and the severity of the reactions. I'll explore the chances of outgrowing each of the most common food allergies. In general, the less severe your food allergy, the more likely you are to outgrow it.

Cow’s Milk

In the United States, cow’s milk allergy affects about 2.5 percent of children during their first two years of life. Fortunately, most kids (approximately 80 percent) will eventually outgrow their milk allergy, most within a few years of their diagnosis.

Your chance of outgrowing milk allergy depends a great deal on whether your allergy is IgE-mediated or not:

  • Non-IgE mediated cow’s milk allergy is almost always a transient condition that passes with age. Non-IgE mediated milk allergy typically causes more subtle, delayed symptoms, such as allergic colitis.
  • IgE-mediated cow’s milk allergy is a more stubborn variety that persists in about 20 percent of children, maybe more.

If you or your child has milk allergy, ask the doctor to specify whether it is IgE-mediated or non-IgE-mediated. Outgrowing a non-IgE-mediated milk allergy is almost guaranteed. Time is on your side. If the milk allergy is IgEmediated, then track the levels of M-IgE (milk-specific IgE) from one year to the next and look for a significant drop in M-IgE levels.

Studies show that people with a higher percentage drop in the M-IgE level in a single year are more likely to develop a milk tolerance regardless of how high their M-IgE level when first diagnosed.

In one study, a percentage drop of 50, 75, 90, and 99 percent correlated with a 31, 45, 66, and 99 percent chance of passing a milk challenge, respectively. Once your M-IgE level drops far enough, your doctor may want to consider performing a food challenge to determine whether you’ve outgrown your milk allergy.


In the United States, egg allergy affects about 1 to 2 percent of children. As with milk allergy, however, a majority of kids outgrow egg allergy within a few years:

  • About half of those diagnosed with egg allergy outgrow the allergy within a couple years.
  • About two thirds outgrow the allergy by the time they’re five.
  • Even more children become less sensitive to eggs, even if they don’t completely outgrow the allergy.

As with cow’s milk allergy, the rate at which egg-specific IgE (E-IgE) levels drop may determine the likelihood that a child has outgrown the allergy. In a group of children who developed egg allergy before the age of four, the percentage drop in E-IgE in one year correlated with the likelihood that the child would pass a food challenge performed at that time.

An E-IgE drop of 50, 75, 90, and 99 percent correlated with a 52, 65, 78, and 95 percent chance of passing the food challenge, respectively. As with milk allergy, if your E-IgE level falls sufficiently, performing a food challenge for egg may confirm a developing tolerance for egg.

Wheat and Soy

Although we haven’t performed specific studies on the likelihood of outgrowing a wheat or soy allergy, the prognosis for outgrowing either allergy is very positive:

  • 80–90 percent of those with a wheat or soy allergy outgrow the allergy by the age of five or six years.
  • In a study of children with food allergy and allergy-related dermatitis, 50 percent of the children with soy allergy outgrew it in a year, and 67 percent outgrew it within two years. Only 25 percent of the children with wheat allergy outgrew their allergy within a year, and only 33 percent outgrew the wheat allergy within two years.

As with milk and egg, those who are more sensitive to soy and wheat may have a more difficult time outgrowing their allergies.


Until recently, most food allergy specialists concurred that people rarely, if ever, outgrew a peanut allergy, and almost every study supported that belief. Relatively recently, however, new studies have shown that approximately 20 to 25 percent of people who have peanut allergy eventually outgrow it.

What does this mean for you or your child who’s been diagnosed with peanut allergy? It means that outgrowing peanut allergy is rather unlikely, but don’t give up hope, and don’t let anyone convince you that outgrowing a peanut allergy is impossible.

A substantial percentage of people lose their sensitivity to peanut, so I recommend asking your doctor to reevaluate you or your child at least once a year, at least up to the age of six years:

  • Test PN-IgE levels annually and monitor these levels over time. Low or undetectable levels of PN-IgEa are a pretty good indication that you’ve outgrown a peanut allergy, but about 30 percent of those with low or even undetectable levels of PN-IgE still experience reactions.
  • If you haven’t had a reaction in the past year or two and your PN-IgE level tests below 2 kUA/L, discuss with your doctor the possibility of an oral peanut challenge to determine if you’ve outgrown your peanut allergy.
  • If you pass the peanut challenge, consult with your doctor about eating peanut regularly. Not eating peanut regularly may be a risk factor for resensitization.

The funny thing about a peanut allergy is that if you outgrow the allergy and then continue to avoid peanuts, you may actually be more likely to become allergic to peanuts again. We performed a follow-up study in 36 patients who had a clear history of peanut allergy.

Of the 36 patients, three of them (8 percent) experienced a recurrence of peanut allergy after having successfully passed a peanut challenge. A six-year-old girl was representative of the three who experienced a relapse. When she was a year old, she ate a peanut butter cracker.

Within five minutes, she broke out in hives and her face swelled up. Her PN-IgE level at diagnosis was 2.79 kUA/L, and she had no history of other food allergies. At age 4.5 years, her PN-IgE level was 1.1 kUA/L, and she passed a peanut challenge.

She subsequently ate only “may contain peanut” products until approximately 1.8 years after the initial challenge. One day, she decided to eat some Butterfinger ice cream. Within 15 minutes of taking two bites of the ice cream, she developed hives, coughing, difficulty breathing, throat tightness, abdominal pain, vomiting, and diarrhea.

A repeat PN-IgE level was greater than 100 kUA/L. All three patients who relapsed after successfully passing the peanut challenge consumed concentrated peanut products less than once a month. In other words, the patients who relapsed had avoided peanuts!

In contrast, none of a group of 23 patients who ate peanut more frequently after having passed their peanut challenge had recurrent peanut allergy. Thus, infrequent exposure may be a risk factor for re-sensitization. This may also be why recurrence is virtually unheard of with other common food allergies, such as milk and egg.

Even if you hate milk after outgrowing your allergy, you’re probably getting some form of concentrated milk on a regular basis, because it’s such a common ingredient. Tree nut allergy may actually be tougher to outgrow than peanut allergy, although few studies prove it.

In our own study, we found that about 9 percent (9 of 101) children with tree nut allergy outgrew their allergy. The rate of resolution corresponded to the TN-IgE (tree nut specific IgE) level:

  • TN-IgE level below 5 kUA/L, 58 percent resolution.
  • TN-IgE level below 2 kUA/L, 63 percent resolution.
  • Undetectable TN-IgE level, 75 percent resolution.

As with peanut allergy, monitor your TN-IgE level closely from one year to the next. If the TN-IgE level drops below 5 kUA/L, consult with your doctor to determine if a tree nut challenge would be advisable.


Allergies to sesame, sunflower, or other types of seeds tend to persist, although no studies provide conclusive evidence to support this. Your doctor may want to monitor your IgE levels for sesame and perform a sesame challenge if your IgE level drops, but we have no specific sesame-specific IgE levels or percentage drops to recommend for testing.


Milk, egg, and peanut are the main players in childhood food allergies. Wheat, soy, and sesame play relatively minor roles. Some other foods make cameo appearances. These include certain fruits, vegetables, and cereal grains other than wheat.

Fortunately, most kids outgrow allergies to fruits, veggies, and grains within a period of six to 12 months. Many of the reactions may represent intolerances or irritant reactions rather than true food allergy. Of course, in at least a few cases, children do develop severe IgE-mediated allergies to these foods that may persist.

I haven’t said much about seafood (fish and shellfish) up to this point, because seafood allergies more commonly develop later in life. In any event, seafood allergies are perhaps the most tenacious of the bunch. Estimates of seafood allergy resolution range from 3.5 percent for fish to 4 percent for shellfish.

Multiple Food Allergies

Some kids seem to be allergic to everything — milk, egg, wheat, peanut, you name it. You may think that these poor kids are just destined to remain allergic to everything. Well, that assumption holds some truth — as a general rule, multiple food allergies may slightly reduce your ability to outgrow any food allergy.

But an inability to outgrow one food allergy doesn’t affect your ability to outgrow a different food allergy. We found this rather surprising. When we began our studies, we predicted that if a child could not outgrow a food allergy that was relatively easy to outgrow, such as milk or egg, the child would never outgrow a stubborn peanut allergy.

Boy, were we wrong. Several children we studied had persistent milk or egg allergy but managed to lose their peanut allergy. Go figure. Your chances of outgrowing one food allergy has nothing to do with your ability or inability to outgrow another food allergy.

Monitor all your food-specific IgE levels and treat each food allergy as a separate condition. Having other allergic conditions, such as asthma or eczema or hay fever, may also reduce the chance of outgrowing a food allergy. In other words, a child with just food allergy may have better odds of outgrowing his food allergy than a child with food allergy plus asthma or eczema.

Most children, however, have other allergy-related conditions in addition to their food allergy, so studying food allergy in isolation is a bit difficult. The results of our studies showed that the presence of other allergic conditions reduced the chances of outgrowing some food allergies, such as milk, but the presence of other allergic conditions did not affect the likelihood of outgrowing peanut allergy.

Speculating on the Timing

When patients and their parents hear the good news that food allergies can be outgrown, they often ask how long it’ll take — a year, two years, five years? Timing is tough to predict. Some children outgrow a milk allergy before they’re out of diapers. Others have to wait until they get their driver’s license.

A number of less fortunate food allergy sufferers never seem to shake their allergy. Nobody can accurately predict the date and time you can expect to outgrow your food allergy or even guarantee that you’ll outgrow it, but I can give you a general idea of what to expect based on IgE levels and exposure:

  • In our studies, the best predictor of timing is the level of food-specific IgE. For example, consider three two-year-olds with milk or egg allergy who have IgE levels (RASTs) of 1, 15, and 75 (all on a scale of 0 to 100). The child with the level of 1 is likely to outgrow the food allergy very soon, if she hasn’t done so already.

The child with the level of 15 could still outgrow her allergy, but it’ll probably take her at least three years. The child with the level of 75 is unlikely to outgrow her allergy, but if it were to happen, it would take at least five to seven years.

  • Another predictor is how a patient responds to a food challenge or accidental exposure. If a child reacts to a tiny exposure, for example, especially if it is a significant reaction, he is likely to be at least a few years away from outgrowing the allergy, no matter what the other test results say. On the other hand, someone who tolerates more of the food before reacting is logically closer to losing the allergy.

These predictors are just that — indications of the likelihood of outgrowing a food allergy in a certain period of time. They offer no money-back guarantee. Some people with undetectable levels of a food-specific IgE may continue to react to the food.

Food allergies are like uninvited guests who stay long past their welcome. So, how do you get them to leave? The best advice I can offer is based on the best information we currently have — strictly avoid the problem food. In practice, some children rapidly outgrow their food allergies without strict avoidance, while others fail to outgrow their food allergies despite the most stringent diets.

Because strict avoidance is so difficult, understanding the impact of continued exposure on the natural history of food allergy would be helpful. However, until we do, the majority of children with food allergy are more likely to benefit from strict avoidance, at least to dodge symptoms and hopefully to hasten the departure of their food allergies.

Strict avoidance has been the mainstay of food allergy management and continues to be the best treatment approach to prevent reactions, keep the condition from worsening, and hasten the process of becoming allergy-free. This advice, however, may change in the future, as we gather more data and explore other treatment options.

Monitoring and Managing Your Allergies

You and your doctor should keep an eye on your food allergies and tweak the treatment approach as your body adjusts. This is particularly important when treating food allergies in children, because children are more likely to outgrow their food allergy and because they’re more dependent on certain foods for normal growth and development.

To stay abreast of the changing nature of food allergies in your child, work with your doctor to:

  • Ensure proper nutrition, growth, and development.
  • Track accidental exposures and reactions to ensure that avoidance measures are adequate and that you’re recognizing reactions promptly and treating them appropriately.
  • Have sufficient supplies of fresh emergency medications, including epinephrine autoinjectors, for home and for your child’s daycare, school, and wherever else she spends time.
  • Ensure that all caregivers understand the allergy management plan and emergency medical treatment plan. Your doctor should provide you with an allergy management plan in writing.
  • Evaluate your child regularly to determine whether she’s outgrown her food allergy. In our clinic, we typically test once a year, but longer or shorter intervals may be more appropriate is some situations. A child with a reaction to fruit, for example, may be evaluated every six months, whereas an older child with persistent peanut allergy may not require annual testing after the first few years if he shows no sign of improvement.

Your child’s allergist may choose any of several methods to evaluate your child for the disappearance of food allergy, including information on accidental exposures, skin-prick testing, in-vitro testing, or blood tests. No single method has proven most effective.

In our clinic, we typically rely on clinical history and CAP-RAST (FEIA) testing to monitor food allergy progression in our patients. We generally do not perform repeat skin testing, because we think it doesn’t change our management in the majority of cases, although other centers perform repeat skin testing on a regular basis.

If a child hasn’t had a reaction in the past six to 12 months, I recommend that the child be re-evaluated in the following ways based on the problem food:

  • IgE-mediated cow’s milk or egg: About 50 percent of children who have a milk or egg allergy shake the allergy by the age of 6 years old. We recommend retesting yearly with CAP-RAST testing. The rate of decline can predict the likelihood that a challenge will be negative. We usually offer a food challenge for milk and egg when the M-IgE or E-IgE level is less than 2 kUA/L, which gives the patient an approximately 50 percent chance of passing the challenge.
  • Non-IgE-mediated milk or egg: Kids tend to outgrow non-IgE-mediated milk and egg allergies more quickly. If the child has had no recent reactions from accidental exposure, a careful challenge is warranted by the age of two or three years old. Be careful, though.

If your child has been diagnosed with food-protein induced enterocolitis syndrome (FPIES), reintroducing milk or egg poses a significant potential risk. Prior to reintroducing milk or egg, your doctor should perform a careful food challenge under close supervision in a hospital setting.

  • Peanut or tree nuts: If you have a peanut or tree nut allergy, consult your doctor to obtain annual CAP-RAST testing. If your TN- or PN-IgE level is less than 2 kUA/L, you and your doctor may consider a supervised challenge. If the challenge confirms that you’ve outgrown your peanut or tree nut allergy, your doctor may advise you to eat the problem nut at least once a month to prevent re-sensitization.

We don’t know the optimal amount you should eat, but we generally recommend a single serving — for example, the amount of peanut in a peanut butter sandwich or a candy bar with nuts. Follow up with your doctor for at least a year to ensure that you’re not experiencing recurrent symptoms.

In patients with persistent peanut allergy, or if the CAP-RAST remains unchanged for several years, less frequent testing is usually sufficient.

  • Wheat and soy: Children usually outgrow their wheat and soy allergies more quickly than allergies to milk or egg. If your child has a wheat or soy allergy, see your doctor yearly for reevaluation with CAP-RAST testing.

When wheat- or soy-specific IgE levels are low, you and your doctor may consider attempting a supervised food challenge. “Low” levels for wheat and soy are not as well-defined as they are for other common allergenic foods.

  • Other foods: If you’re allergic to some other food not included in this list, we recommend annual evaluations and testing. As mentioned previously, repeat evaluation can be less frequent if the allergy is showing little sign of improvement.

Testing negative doesn’t mean you’ve outgrown your allergy, nor does testing positive mean that you still have it. A negative test merely enables you and your doctor to gauge the likelihood that you’ve outgrown your food allergy and that a food challenge may be safe and useful.

Only by successfully passing a food challenge can you be certain that the allergy is gone. Never perform a food challenge on your own — proceed with caution under your doctor’s supervision, and with full emergency equipment and medications on hand to treat possible reactions.

Safely Reintroducing the Problem Foods

Say you’ve managed to raise your child with a severe food allergy for a couple years. You’ve mastered the fine art of avoidance. Your kid doesn’t mind not eating a particular food. In fact, he seems to dislike the food. Why would you even consider taking the risk of re-introducing the problem food? Why not leave well-enough alone?

I have several good answers to offer for that question:

  • Knowing that your child has outgrown the food allergy can reduce your family’s anxiety.
  • Your child automatically increases the variety of foods he can safely consume.
  • By not knowing that your child has outgrown the food allergy, you may increase the risk that your child will become re-sensitized to the food.

Based on your child’s history, the severity of past reactions, the most recent test results, and the problem food, your doctor may decide that your child is ready for a food challenge or for you to try to re-introduce the food at home (if the risk of a severe reaction is very low).

If your doctor recommends that you re-introduce the problem food at home and you’re not comfortable doing that, request a supervised food challenge in the doctor’s office. If your child passes the food challenge without incident, you’re likely to be less worried about adding the food to your child’s diet.

I rarely recommend introducing the food at home if the child has a peanut allergy or has had acute reactions to the problem food until the child passes a food challenge. Although CAP-RAST tests provide a fairly good indication of whether you’ve outgrown an allergy, they offer no guarantee.

You can have low food-specific IgE levels and still experience an allergic reaction, or you can have relatively high food-specific IgE levels and safely consume the food. The only way to be certain that you’ve outgrown your food allergy is to try eating the problem food — challenge your system.

The problem with challenging your system with a food that has made you ill before is that it can be somewhat risky, particularly if you experienced severe reactions in the past. To increase safety, we normally perform a food challenge in our clinic under doctor’s supervision with emergency equipment and medication on hand.

What can you expect from a food challenge? A food challenge typically proceeds as follows:

  1. Your doctor or your doctor’s assistant feeds you a specific amount of the problem food that you’re likely to tolerate.
  1. You sit in the room for a period of time under close observation for any signs of a reaction. (If you react, the doctor or assistant obviously treats you for the reaction.)
  1. Pass the food challenge, and the doctor sends you home with instructions for safely re-introducing the food at home. Usually you start with the amount of food that you ate during the food challenge and then gradually ramp up the dose over the course of a week or more.

If your doctor recommends introducing the food into your child’s diet at home, follow the doctor’s instructions carefully and proceed slowly. Gradually increase the amount of the problem food in the diet over the course of 1 to 2 weeks.

When introducing milk into the diet, I typically advise parents to start with one teaspoon on the first day or two and then double the dose every one to two days. If you get up to 4 to 6 ounces in a day with no reaction you’re probably home free. Once you can tolerate a full serving of the food over a period of several days, your doctor is likely to lift all restrictions, so you can consume all forms of the food.