The Link Between Asthma and Food Allergies

Asthma and food allergies may be more closely linked than previously thought. Even beyond the fact that people with food allergies are at higher risk of developing asthma than people without them, there is evidence that having asthma increases the risk of a severe allergic event—including a potentially life-threatening, whole-body reaction known as anaphylaxis.

A growing body of research suggests that asthma and food allergies are part of a larger cluster of disorders known as the "atopic march" in which one atopic (allergic) disorder gives rise to another. This can not only alter how asthma and food allergies are treated but also offer a means by which to potentially prevent both diseases early in life.

Prevalence

The relationship between asthma and food allergies is a complex one. According to a 2017 study in the Frontiers of Pediatrics, between 4% to 8% of children with asthma have a food allergy, while roughly 50% of children with a food allergy will experience respiratory symptoms during an allergic reaction, including wheezing and shortness of breath.

Although the incidence of food allergy in children with asthma is not all that different from the incidence seen in children in the general population, which also hovers at around 8%, they tend to be harder hit by a respiratory event when allergy strikes.

A 2016 review of studies from Italy concluded that asthma is not only a risk factor for a severe anaphylactic reaction to foods but is the main cause of death in children with food anaphylaxis.

The risk of anaphylaxis appears closely linked to the severity of asthma. Research suggests that people with mild asthma are at double the risk of anaphylaxis compared to people in the general population, while people with severe asthma are at more than three times the risk. The risk is even greater in people with both asthma and food allergies.

By Asthma Type

Despite asthma being an atopic disorder, not all forms of asthma are allergic. The relationship between asthma and food allergies seems to differ based on this.

According to a 2020 study from Finland, the number of allergic and non-allergic asthma diagnoses in a random cohort of patients were almost equally split, with 52% having allergic asthma and 48% having non-allergic asthma.

What makes the finding especially interesting is that the prevalence of food allergies in these individuals closely matched that of allergic asthma but not non-allergic asthma.

Food allergies tend to develop in early childhood⁠ (before age 9⁠), affecting fewer and fewer children over the years as they "outgrow" their allergies. It is a downward trend that continues through adulthood, only increasing in numbers after the age of 60.

Similarly, with allergic asthma, children between the age of 9 and younger are the group most affected by the disease, with numbers steadily declining into adulthood and only increasing after 60.

With non-allergic asthma, the pattern is just the opposite. With this disease, the fewest number of cases are seen in early childhood, after which there is a steady increase in the number of cases until the age of 60, when numbers drop.

Symptoms: Differences and Overlaps

There is some overlap in the symptoms of asthma and food allergy. However, with food allergies, respiratory symptoms almost never occur on their own. Rather, they are either preceded by or accompanied by skin and gastrointestinal symptoms.

When asthma symptoms occur with an acute food allergy, they will almost invariably make the reaction worse and, in some cases, lead to anaphylaxis.

Breathing difficulties in people with an allergic food reaction are sometimes mild, manifesting with transient episodes of shortness of breath. In other cases, they may start mildly but progress over the course of minutes or hours into a full-blown anaphylactic emergency.

Symptoms of anaphylaxis include:

• Rash or hives
• Shortness of breath
• Wheezing
• Rapid breathing
• Lightheadedness or dizziness
• Flushing
• Rapid heart rate
• Nausea or vomiting
• Difficulty swallowing
• Confusion
• Swelling of the face, tongue or throat
• A feeling of impending doom

Causes

Atopic disorders, of which asthma and food allergy are just two, are those in which a person has a genetic disposition toward an allergic or hypersensitive reaction. While the terms allergy and hypersensitivity can be used interchangeably, an allergy refers to the clinical reaction while hypersensitivity describes the underlying immunologic response.

Although food allergies strongly predispose a person to asthma, the two diseases are believed to be part of a longer chain of conditions. Atopic march, sometimes referred to as the allergy march, describes the natural progression of atopic diseases as one leads to another.

Atopic March: A Domino Effect

Atopic march generally starts early in life in a classic pattern. In most cases, atopic dermatitis (eczema) is the condition that instigates this. It tends to occur very early in life, usually before the age of 3, in children who will later develop allergies.

Atopic dermatitis occurs when the barrier function of the skin is compromised, allowing substances (both harmful and harmless) to enter the body before the immune system is mature. Genetics is believed to play a central role in the reduced barrier function.

When these substances enter the body, the immature immune system over-responds and floods the body with antibodies known at immunoglobulin E (IgE). IgE not only helps neutralize the perceived threat but leaves behind "memory" cells to sentinel for the return of the threat and respond quickly if it is detected.

Even when the immune system is fully mature, the immune response will have already been altered. This can make the body hypersensitive to newly introduced foods, such a cow's milk, eggs, or nuts, manifesting with one or more food allergies.

The hypersensitivity to food allergens, in turn, instigates changes in the immune response that may increase a person's sensitivity to inhaled allergens, leading to allergic rhinitis and asthma.

As with food allergies, the risk of asthma is closely linked to the severity of atopic dermatitis. According to a 2012 review in the Annals of Allergy, Asthma, and Immunology, only 20% of children with mild atopic dermatitis will go on to develop asthma, while over 60% of those with severe atopic dermatitis will.

In the end, atopic dermatitis is the common denominator that links food allergies to asthma.

Common Food Triggers

Food triggers can be characterized by the general age of allergy onset and the general age by which reactions tend to resolve.

Fish and shellfish allergies tend to develop later in life because they are often only introduced into the diet after early childhood.

Food triggers can cause exacerbations in those with asthma, but can also have a variety of other effects.

Non-Allergic Asthma Cases

All of this said, it should be noted that not all children with asthma are equally affected by food allergy. While the severity of asthma may play a part, the type of asthma a person has may also contribute.

Non-allergic asthma types have different biological mechanisms that provoke an asthma attack. As such, some with non-allergic asthma may only experience a mild itch during an allergic reaction (to a food or other allergen) with no respiratory symptoms at all.

Unlike allergic asthma, non-allergic asthma is triggered more by stress, exercise, cold, humidity, smoke, and respiratory infections than by food or food allergens. Certain medications and food additives can provoke an attack, but the response is related more to a non-IgE intolerance than an outright allergy.

Diagnosis

Food allergy testing is considered vital to the identification of food allergies in children and adults with allergic asthma. There are limitations to the tests, however, most especially in young children.

Children Under 5

In infants and toddlers, food allergy tests have a high rate of false-positive results and can provoke changes in diet that are not only unnecessary but detrimental to the health of the child (i.e., they may limit nutrients important for growth and development).

Because of the limitations of the tests, the American Academy of Pediatrics (AAP) recommends that food allergy testing only be pursued in infants and toddlers if symptoms of food allergy occur within minutes to hours of eating food.

The two allergy tests recommended for children under 5 are:

• IgE blood test panels that can detect a variety of food-specific IgE antibodies (most specifically, milk, egg, peanut, wheat, and soy, as these are the food allergies most commonly experienced in infants and toddlers)
• Oral challenge tests in which suspected foods are fed to the child under controlled conditions (i.e., in a doctor's office or hospital) to see if a reaction occurs

Other forms of food allergy testing are not recommended for children under 5.

Older Children and Adults

For these individuals, the following tests may be used alongside IgE blood tests and food challenges:

• Skin prick testing, in which tiny amounts of food allergens are placed under the skin to see if a reaction occurs
• Elimination diets, in which foods are temporarily removed from the diet and then gradually reintroduced one-by-one to see if an allergy occurs

There are other tests used by some practitioners that are not recommended by the AAP or the American Academy of Allergy, Asthma & Immunology (AAAAI). These include food IgG testing, applied kinesiology, provocation neutralization, hair analysis, and electrodermal testing. None of these have any scientific evidence to support their use in the diagnosis of a food allergy.

Always seek care from a board-certified allergist/immunologist if you are seeking the diagnosis or treatment of a severe allergy.

Treatment

If you have asthma and food allergies, efforts will be made to manage both of your conditions. The aims of the treatment plan are twofold:

• By keeping your asthma under control with controller medications, the hyperresponsiveness of the airways can be reduced along with your sensitivity to asthma triggers.
• By identifying your food triggers, you can learn to avoid them and have medications on hand to prevent a severe reaction if accidental exposure occurs.

This is important regardless of the extent to which your asthma symptoms are affected by food allergens, although it's especially important if you experience severe reactions.

For Asthma

The choice of asthma medications depends largely on the severity of your asthma symptoms. Mild intermittent asthma may only require a rescue inhaler to treat acute attacks. Persistent asthma may require controller medications that reduce airway hyperresponsiveness and inflammation.

Among the standard options for asthma treatment are:

• Short-term beta-agonists (SABAs), also known as rescue inhalers
• Inhaled corticosteroids (steroids), used daily to reduce inflammation
• Long-term beta-agonists (LABAs), a bronchodilator used daily with inhaled steroids to reduce hyperresponsiveness
• Leukotriene modifidiers like Singulair (montelukast)
• Mast cell stabilizers like cromolyn sodium and nedocromil
• Theophylline, an older drug sometimes used as an add-on when treatments underperform
• Biologic drugs like Xolair (omalizumab)
• Oral corticosteroids, typically prescribed for severe asthma

In addition to these asthma-specific medications, over-the-counter antihistamines may be considered. Antihistamines are sometimes prescribed daily during hay fever season to prevent a severe asthma attack in people with a pollen allergy. There is evidence that the same approach may be beneficial to people with asthma and food allergies.

A 2012 study from Sweden reported that children with severe pollen allergies are a greater risk of food anaphylaxis than those without them.

It serves to reason that a daily antihistamine during hay fever season may reduce the risk of a severe asthma event if food allergy and seasonal allergy co-exist. Speak to your doctor, particularly if you have a history of anaphylaxis.

For Food Allergy

In the absence of allergy testing (or a definitive allergy test result), efforts need to be made to identify which foods you are allergic to. One way to do this is to keep a food diary that lists all of the foods you have eaten during the day along with any abnormal symptoms you may have experienced.

Because many allergens like nuts, wheat, and dairy are hidden in prepared foods, a food diary can help you pinpoint which items most commonly cause symptoms. You can then check product labels to see if suspect allergens are listed in the ingredients.

In the end, any respiratory symptom that accompanies a food allergy should be taken seriously. In some cases, a food allergy can evolve over time and manifest with ever-worsening symptoms. In other cases, the amount of an allergen consumed can make the difference between a non-anaphylactic event and an anaphylactic one.

If you have a history of acute respiratory symptoms during a food allergy, your doctor will likely prescribe emergency injector pens, called EpiPens, that contain a dose of epinephrine (adrenaline). When injected into a large muscle, an EpiPen can quickly reduce the symptoms of anaphylaxis until emergency help arrives. A rescue inhaler may also be used after the epinephrine shot to keep the airways open.

Prevention

There is evidence that introducing foods like peanuts and eggs to a baby's diet as early as 4 to 6 months can reduce a child's risk of developing food allergies.

Similarly, using the appropriate daily moisturizer or cream on infants and toddlers can help maintain the barrier function of the skin and reduce the risk of atopic dermatitis. Doing so may prevent the onset of the atopic march.

In theory, by stopping the atopic march before eczema or food allergies develop, a child will be less likely to develop allergic rhinitis or asthma. However, this is not a guarantee.

Coping

Living with asthma and food allergies can be complicated, but there are things you can do to better cope and avoid the trigger than can lead to a severe attack. Among the recommendations:

• Take asthma medications as prescribed. Adherence to daily medications in people with asthma is generally lacking, with around 66% of users reporting poor adherence. By taking your medications every day as prescribed, you can reduce your sensitivity to asthma triggers as well as the risk of food anaphylaxis.
• Learn to read ingredient labels. Under the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA), food manufacturers are required to list all eight common food allergen on their ingredient labels. Checking labels can help you avoid hidden allergens.
• Avoid cross-contamination. If you have a severe food allergy, even the smallest amount of an allergen can cause an attack. To avoid cross-contamination, keep surfaces clean, store allergen-containing foods in separate sealed containers, do not share utensils, and wash your hands frequently.
• Check menus before dining out. Always review a restaurant's menu online before dining out. If you don't know what is in a dish, ask. Better yet, tell your server about your allergy so that mistakes can be avoided or adjustments can be made. Never share food with your fellow guests.
• Always carry your EpiPen. Most life-threatening anaphylactic emergencies are the result of a missed epinephrine dose. Always keep your EpiPen with you, and teach loved ones how to give the injection if you can't.

A Word From Verywell

Neither asthma nor food allergies are fixed conditions. Both can progress over time and require changes in treatments to maintain control of symptoms. At the same time, certain food allergies can spontaneously resolve and no longer pose a risk to your health.

By seeing your doctor regularly, you can receive the appropriate treatment for both your asthma and food allergies so that neither are under- or over-treated. Consistent medical care almost invariably improves the long-term control of asthma symptoms.