Food Allergies and Asthma

Although the true incidence of food allergies is unknown, a recent study suggests that about 5% of the population may suffer from adverse reactions to food. In this section, we will discuss about food allergies and asthma.

Food Allergy Symptoms:

Vomiting, nausea, stomach cramps, indigestion, diarrhea, hives, eczema, headaches, asthma, earaches and rhinitis (itchy, stuffy, runny nose; sneezing, and phlegm in the throat) are among the most common symptoms. In fact, many parts of the body can be affected by food allergies. The frequency and severity of symptoms vary widely from one person to another. Highly allergic persons may experience severe and life-threatening reactions such as upper airway swelling of the tongue and lips while, in milder cases, other may only suffer a minor case of sniffles. Not all adverse reactions to foods are due to allergy. Some reactions to milk, for example, are related to a deficiency of an enzyme (lactase) which normally breaks down a sugar in milk (i.e. lactose). This deficiency in some individuals causes a reaction similar to food allergy when milk is ingested.

What foods are most likely to cause allergy?

Eggs, milk, nuts, soy, seafood, fish, corn and wheat are the most common allergy- causing foods, but almost any food can cause allergy. Keep in mind that, if you are allergic to a particular food, you might be allergic to related foods. For example, a person allergic to milk also may react to confectionery products. Likewise, a person allergic to peanuts often cannot tolerate other members of the legume family whose members include peas and beans.

Food Allergy Testing and Diagnosis:

Food allergy testing and diagnosis is typically done using multiple approaches. Some of these include:

1. History

The starting point for food allergy testing and diagnosis is the history – a record of your symptoms. Your doctor will look for clues in your lifestyle that will help pinpoint the cause of your problem. You’ll be asked about your work and home environments, your eating habits, your family’s medical history and miscellaneous matters, such as what kind of heating and cooking fuels you use, and if you have pets! A lot depends on how observant you are. If you suspect your symptoms to be due to a particular food item, then every time you consume that, the symptoms of asthma should appear within a few hours.

2. Skin Prick Test

Skin prick test is a sensitive tool to detect food allergy. In prick test, small amounts of the suspected allergen are introduced into the skin. A positive reaction – a wheal, swelling or flare in the surrounding red area – indicates the presence of allergic antibodies. However, skin tests are useless in diagnosing food allergy. Although many allergists carry out skin tests with food allergens, their utility in establishing the diagnosis is questionable.

3. RAST Test

Some patients are given RAST test, which use blood samples to determine the extent of antibody production against an allergen. Again, the value of RAST test in diagnosing food allergy is not established.

4. Elimination Diet

Elimination diet starts with with a limited set of ‘tolerant’ foods. Over a period of days or weeks, other foods are added one after the other. Although time-consuming, elimination diet can be an effective way to judge which food substances are problematic when skin prick test is inconclusive.

5. Double blind food challenge test

With the information gained from your history, your allergist may further narrow down the suspected foods by placing you on a special diet. Your allergist may ask you to keep a daily food diary listing all food and medication ingested, along with your symptoms for the day. By comparing “good days” with “bad days,” you and your allergist can determine which foods are prime suspects. Tests to confirm whether true food allergy is present are then carried out. A double blind testing means that neither the patient nor the doctor knows which food item is being tested. The suspected food item is given in very small quantity in a capsule. Following a baseline lung function test, the capsule is ingested. Following this, lung function tests are carried out at regular intervals for a few hours to see if asthma develops. If not, a higher dose is given the next day and the procedure is repeated. In this manner, it is confirmed whether or not the patient is allergic to a particular food. This is the only sure way of proving food allergy.

Then you may be asked to follow a trial diet, which alternates days of consumption and avoidance of suspected foods. If your symptoms subside during abstinence-and flare up when you eat the food again-the problem food has been identified.


Avoidance of the allergenic food is the best policy. You must be vigilant in checking ingredient labels of food products to make sure an offending food or food additive is not present. For example, a person allergic to milk must avoid ice cream, cheese, chocolate bars and many cake mixes.

If you have a severe immediate-type reaction to certain foods, NEVER taste them again. In some very sensitive persons a small taste of an allergenic food can produce a life-threatening reaction.

However, if your symptoms are milder, you may be able to try a problem food again. After you have abstained from allergenic foods for a period of at least six months or longer, your allergist may suggest that you try a small portion of a problem food. If you have no reaction, you may be able to eat this food occasionally and in moderation. Allergic reactions to foods have been known to disappear for months or years, then reappear. In some cases, the allergy disappears for good.

Desensitization – the practice of injecting small quantities of the suspected food item solutions repeatedly over several months and years is a dangerous practice. Not only is it absolutely useless, it can even cause life-threatening reactions.

Remember to take your inhaler regularly. Even if you are allergic to a particular food, it could be only one of the many triggers of asthma. Avoidance of the food item will prevent asthma only due to that trigger. Some notes:

  • Asthma due to food allergies is much less common than what the patients believe it to be.
  • Many patients with asthma stop taking foods like milk, banana, curds rise and eggs believing that these are bad for asthmatics. In most cases, these turn out to be false assumptions.
  • If you believe or suspect that your asthma symptoms are due to a particular food item, tell your doctor about it. He will be able to confirm or remove your doubts. Do not stop eating the suspected food item without confirming that it is indeed the cause.
  • A nutritious and balanced diet is as essential for asthmatics as it is for any healthy person.

Do not impose unnecessary restrictions on types of food items you consume.

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