Food allergy

What is a food allergy?

There are various kinds of allergy triggers, including dust mites, mold, pollen, and food. A food allergy is when a particular food enters your body and triggers an allergic reaction.
At times, symptoms may occur just by touching food or inhaling its scent.

Food allergy symptoms

Food allergy symptoms often appear on the skin. Itching, redness, hives, and rashes are common. Other symptoms include gastrointestinal discomfort such as abdominal pain and diarrhea, respiratory problems such as coughing, wheezing, and difficulty breathing, and irritation of the mucous membranes such as the eyes and nose.

What is anaphylaxis?

Anaphylaxis describes a state where allergy symptoms manifest in at least 2 organs, such as the skin, digestive organs, respiratory organs, etc.
Anaphylactic shock occurs when anaphylactic symptoms progress and blood pressure drops. This is a life-threatening state. You may feel faint or lose consciousness. In Japan, about 3 people die each year from anaphylactic shock. Swift, appropriate treatment is critical.

Next: Food allergy types

Food allergy types

1. Immediate onset

Symptoms appear within an hour or 2 after ingesting the food.
In most cases, symptoms appear within 15 minutes. The symptoms may be varied: Hives all over your body, coughing, wheezing, difficulty breathing, vomiting, diarrhea, etc. In some cases, you may progress from an anaphylactic state into anaphylactic shock.

Age of onset

This type of food allergy can occur for the first time at any age. However, onset during infancy and early childhood is seen extremely often.

Trigger foods

Infancy to early childhood: Eggs, milk, wheat, fish eggs, peanuts etc.
School age and older: Shellfish, fruit, wheat, fish, etc.

Symptoms

Please refer to “Food allergy symptoms.”

Condition over time

Although eggs, milk products, wheat, and soy are common triggers of immediate-onset food allergies in infants, many children seem to outgrow these allergies naturally. About 50% of children are able to eat these foods by age 3, and 80% to 90% by age 6.
On the other hand, trigger foods such as peanuts, soba buckwheat, fish, and fruits are not easily outgrown. Long-term, or lifelong, elimination is sometimes required.

2. Infantile atopic dermatitis associated with food allergy

Age of onset

This type of food allergy manifests during infancy in association with atopic dermatitis, and is outgrown as the child ages.

Trigger foods

Eggs, milk, wheat, soy etc.

Symptoms

Rash

Course of the condition

After early childhood, the involvement of food allergy as a cause of atopic dermatitis decreases.

3. Neonatal-infantile gastrointestinal allergy

Age of onset

This type of food allergy manifests in newborns and young infants as bloody stool, diarrhea, vomiting, and other symptoms of the digestive tract. It is believed to be a cell-mediated immunity response.

Trigger foods

Milk (including formula), soy, rice, etc.

Symptoms

Gastrointestinal symptoms appear within several hours to a few days after ingesting the trigger food. Symptoms are mainly of the digestive tract, such as vomiting, diarrhea, and bloody stools.

4. Atypical food allergies

(1) Oral allergy syndrome (OAS)

Symptoms appear when trigger foods come into contact with the mucous membrane of the mouth. Cross-reacting allergens in pollen and fruits may trigger this response in hay fever sufferers. Onset occurs more frequently in school-age children.

Trigger foods

Fruits (kiwi, apple, peach, melon) etc.

Symptoms

After eating the trigger food, in many cases symptoms appear swiftly in the mouth and/or throat (itching or burning sensation in mouth, scratchy throat, swollen lips, etc.). In rare occasions, anaphylaxis may occur.

(2) Food dependent exercise-induced anaphylaxis (FDEIA)

This type of allergy is characterized by occurring only when a certain level of exercise is done after eating a trigger food. It is often seen in older children (10 years and older), as exercise tends to increase at this age, and adults.

Trigger foods

Wheat 60%, shellfish 30%, other

Symptoms

Symptoms appear only when a certain level of exercise is done within 2 to 4 hours of eating the trigger food. Symptoms progress rapidly and anaphylaxis is not uncommon.

Food allergy diagnosis

In diagnosing food allergies, the most important element is the consultation (patient providing doctor with information). The patient will be asked a series of detailed questions, such as how much of what he or she ate, and what kinds of symptoms appeared how many minutes later.
If the allergy is immediate-onset, it is relatively easy to identify the trigger food and various tests may therefore be omitted. However, for other types of food allergy, the gold standard is food elimination and testing a potential food trigger by trying it.
Blood and skin tests are not diagnostic criteria. They only aid diagnosis.
It is also important to note that, although there is a tendency to suspect food as the cause of infant rashes and atopic dermatitis, this is not necessarily the case. The diagnosis is made after a process of thorough consultation, testing, and objective evaluation of the results.

Next: Treatment

Treatment

1. Elimination of trigger foods

The general rule is to eliminate a minimum range of trigger foods on the basis of a doctor’s correct diagnosis. An elimination diet should be started after thoroughly consulting with your doctor on what foods to eliminate, how to eliminate them, to what degree, and for how long.
For tips on elimination diets, go to this page:What to do

2. Medication

There is no medication which prevents the onset of food allergies or which allows sufferers to start eating trigger foods (develop tolerance). In most cases, the following medications do not need to be used in combination.

(1) Sodium cromoglicate (product name: Oral Intal®)

Indicated only for skin symptoms associated with food allergy. Taking this medicine in no way helps food allergies go away. Neither does it keep symptoms in check to let the sufferer eat small amounts of trigger foods.
For these reasons, it is a good idea to take a look at whether you are practicing the correct skincare and using ointment properly, before taking this medicine.

(2) Antihistamines

Antihistamines are sometimes prescribed to control itching and other skin symptoms of food allergy. However, they can usually be discontinued after proper elimination of the trigger food. Like Intal®, antihistamines do not make food allergies go away. It is also important to remember that antihistamines are only effective in relieving mild symptoms of the skin and mucous membranes. They should not be expected to alleviate symptoms which are moderate or severe, including anaphylaxis.

(3) Treatment of anaphylaxis

If you have had anaphylaxis in the past, or are considered to be at high risk of having an anaphylactic attack, the doctor may prescribe a portable, self-injectable adrenaline preparation (product name: EpiPen®) as a treatment aid. This prescription medication can be injected by the patient, the patient’s guardian, or a paramedic.
Once severe anaphylactic shock symptoms appear, the patient’s life depends on adrenaline being administered within 30 minutes. It is crucial to act swiftly and appropriately. However, the medication only lasts about 10 minutes, and the patient’s condition may become serious. Once you inject EpiPen®, always call an ambulance and go to the hospital.

About EpiPen®

EpiPen® comes in 2 forms (0.15 mg and 0.3 mg) according to the adrenaline content. The 0.3 mg preparation (yellow) is for patients weighing at least 30 kg. The 0.15 mg preparation (green) is for patients weighing between 15 kg and 30 kg.
Make sure you know how to use and store it, so that you will be able to use it properly when you need to.

For emergency procedures please refer to “Emergency procedures page.”