Ask the Ecz-perts: Food Allergies

In Ask the Ecz-perts, leading medical experts answer your most pressing questions about eczema and its related conditions.

In this edition of Ask the Ecz-perts, Ari Zelig, MD, allergist and immunologist at the Asthma and Allergy Associates of Florida, answers questions about food allergies.

Is food-exacerbated eczema mostly linked to serve eczema, or is it in milder forms too?

Food-exacerbated eczema is mostly linked with moderate to severe forms. I tend to look for a possible food allergy when patients have moderate to severe eczema that does not respond to standard of care topical therapies or if eczema notably flares after a specific food is ingested.

If you suspect food-exacerbated eczema, it’s important to use clinical history and the most common culprits for testing (milk, egg, peanut). If an elimination diet is tried, a maximum of three to four weeks is appropriate. If it is food-exacerbated eczema, it should improve in that time frame. If there is no improvement, it’s important to introduce the food back into the diet. Eliminating food allergens for prolonged periods of time can lead to development of immunoglobin E (IgE)-mediated food allergy.

I have had a few dermatologists say that there is no such thing as food allergies. Is this just semantics? What am I missing in these controversial statements? Many say it is not an allergy if it is not anaphylactic. I find it prevents a good discussion when terminology is not even agreed on. If my AD is controlled, will the food allergies go away or improve some so that certain foods can be reintroduced?

When discussing adverse food reactions, there are immune-mediated and non-immune-mediated reactions. The type of reactions most of us are focused on here are IgE-mediated food reactions, which can present with an array of symptoms such as hives, swelling, abdominal pain, vomiting, diarrhea, coughing, trouble breathing, wheezing, drop in blood pressure, fainting and a severe life-threatening reaction known as anaphylaxis. Symptoms typically occur within minutes to an hour of eating a specific food.

IgE-mediated food allergy is very real, affecting 6-8% of children and around 11% of adults. The prevalence food allergies is increasing. To say that it is not an allergy if it is not anaphylactic is false and can provide a false sense of security to patients. In fact, the severity of one food allergy reaction does not necessarily predict the severity of future reactions. Anyone with a history of IgE-mediated food allergy should be evaluated by an allergist and should carry two epinephrine autoinjectors at all times.

It seems possible that some of the doctors you have spoken with may be suggesting that certain symptoms or food reactions are not IgE mediated. Many conditions, such as lactose intolerance and Celiac disease, are not allergic conditions but still certainly require evaluation and treatment.

Unfortunately, food allergies do not tend to improve over time even if the eczema is better controlled. Regarding this topic, though, there are studies showing that aggressive topical therapy in infants with atopic dermatitis was associated with a decrease in later development of food allergies.

I recently went through the food elimination process and discovered that many things cause my eczema to flare up: dairy, gluten, nightshades, etc. Without having confirmed food “allergies,” my doctors aren’t really considering these reactive foods to be true allergies but more as “intolerances.” Is there any way to legitimize these “allergies” more, especially when eating out with family and friends? Are there any specific research studies that I could share with my doctor around this?

Over testing is done too often, and results are misinterpreted. False positive tests lead to unnecessary avoidance. If you are tolerating foods without reaction, I would not test for them; it creates anxiety for no real reason. In “food intolerance” tests, which are available commercially, look for IgG to foods. IgE is the antibody which causes allergic reactions, not IgG. These intolerance tests are not approved by the FDA and are very misleading.

You have probably heard about COVID antibodies. This looks for IgG responses to COVID. If you get an infection with any bacteria or virus, or if you get a vaccine, you develop immune responses or memory to that particular antigen. IgG is that memory. It’s the immune system saying, “Hey, I have seen that before, and I recognize it.” You can send bloodwork for IgG levels from prior vaccines or infections to assess for evidence of immunity.

Now, how does that relate to foods? If you have eaten a food before, you can develop IgG to foods. It does not mean it is causing you harm; it just means your immune system recognizes it. In fact, IgG4 levels to specific foods are protective against IgE-mediated allergy.

IgG4 levels increase with food oral immunotherapy, and IgE to specific foods decrease with food oral immunotherapy. The same is true for how allergy shots decrease allergic responses. I cannot advise strongly enough against these intolerance tests. They are terribly expensive and lead to tons of confusion.

Here are a few resources you can share with your doctor:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3734168/

https://www.aaaai.org/conditions-and-treatments/library/allergy-library/IgG-food-test

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4759210/

Is there any relationship between food intolerances — not allergies — to lactose, fructans, sorbitol, mannitol, etc., and AD?

I do not think there is a correlation here. Lactose intolerance is an enzyme deficiency and not an atopic or allergic issue.

I have been off of many foods for over a decade. No one ever told me that you may never get the ability to add them back into your diet without having negative physical symptoms persist. Can you ever really build up tolerance of a food again?

If you have been avoiding multiple food allergens for years, I would definitely advise seeing an allergist for testing. Based on your history and testing, your doctor will be able to tell you which foods must be avoided, which may be introduced at home and which require an oral food challenge in the office.

It would be helpful to know if you have been avoiding all these foods because of eczema and positive testing, or if you have had clinical reactions to each of these. With eczema and a markedly elevated IgE level, you will get false positive tests (both skin and blood tests), so it is really important to work with an allergist on this. Eliminating multiple foods based on testing alone, without a clinical history of a reaction, can do more harm than good.

How often do food allergies change? And how often should I get tested for them?

It depends on which foods we are talking about. I check annually for children with milk, egg, wheat or soy allergies, as these are often outgrown. Skin tests and blood testing are used, as decreasing wheal size on skin prick and decreasing specific IgE levels indicate the possibility that the food allergy is being outgrown. For nuts and seafood, I usually check less often, like every two to three years or so, as these are less likely to be outgrown.

Can a reaction to a food allergy cause temporary hypersensitivity to other foods?

Many food allergy patients do have more than one food allergy. A couple examples: Infants with an egg allergy should be screened for peanut allergy early in life. Some peanut allergic patients may also be tree nut allergic.

What do you advise when eczema flares in breastfeeding moms?

If eczema is flaring with breastfeeding, I would take a good history of the maternal diet and consider skin testing to major food allergens, again, with the focus on the common offenders (milk, egg, peanut, etc.). If eczema flares with breastfeeding, consider a maternal elimination diet based on diet/history/testing for three to four weeks. If there is no difference in eczema, then reintroduce the food back into the diet.

When is the earliest an infant showing signs of cow milk allergy? How do you recognize it?

IgE-mediated milk allergy often develops in infancy and usually presents with symptoms within minutes to an hour of drinking. Symptoms may include hives, swelling, coughing, trouble breathing, coughing, wheezing, vomiting, diarrhea, drop in blood pressure, and in severe cases, can present with anaphylaxis. Cow’s milk formula is the common trigger, but infants who are highly sensitized and breastfed can react to milk in the maternal diet.

There is a condition known as proctocolitis which occurs in infancy most often. These children present with bloody or mucousy stools but no other symptoms. This is a non IgE-mediated condition. It is usually outgrown around one year of age and these children often need special hypoallergenic, hydrolyzed formulas.

FPIES is another non IgE-mediated condition that can occur in infancy and is a severe, delayed GI reaction. Usually about two to four hours after eating, patients have vomiting, diarrhea, and in severe cases, can experience a drop in blood pressure. There is a rarer chronic form which can present with gastro-intestinal symptoms and failure to thrive.

My 10-year-old is allergic to dairy, eggs, peanuts and tree nuts. She reacts atopically. I have a 9-month-old son that was switched to hypoallergenic formula from dairy/soy formulas because of traces of blood in his stool. Is this a common “allergy diagnosis” in formula-fed infants? When should we get him tested?

The diagnoses here is proctocolitis. This is non IgE mediated and occurs most often with cow’s milk and soy. It usually is outgrown by one year of age. I would consider skin testing to milk prior to reintroduction. Some children can also develop a coexisting IgE-mediated food allergy to milk. With the family history, it is probably worth skin testing prior to the reintroduction trial since it will have been avoided for quite a while.

Ari Zelig, MD, allergist and immunologist, Asthma and Allergy Associates of Florida

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