Delayed
immune reactions to food
Introduction
Conditions such as eczema, vomiting, sloppy poos and irritability
are very common in babies and infants. Most are not due to allergic
or other reactions to food, but some are. This article provides
an overview, with an emphasis on babies and infants with possible
food reactions.
Allergic reactions to food: overview
"Immediate" (rapid onset) allergic reactions to
food affect around 1 in 30 infants, and are relatively easy to
diagnose. Symptoms of hives or vomiting usually occur within an
hour or less after eating, and allergy testing is almost always
positive.
Occasional children, however, do NOT have reactions that occur quickly. Instead, delayed immune reactions start after several hours or days, most commonly in response to dairy products, soy or wheat. Patients generally present with one or more of severe atopic dermatitis/eczema, chronic diarrhoea, failure to thrive, or severe reflux of food or formula. Symptoms occur due to inflammation of the skin or gut, and results from attraction of white cells from the blood into the tissues.
Routine allergy testing is often negative, making diagnosis more difficult. Diagnosis usually rests on the history of possible reactions to food, and responses to food withdrawal and re-challenge. Most of these delayed reactions resolve by the age of 3 years. At times, even small amounts of food allergen passing through breast milk can aggravate eczema or gut symptoms. Allergy testing of the infant may or may not be positive, depending on the mechanism of the sensitivity (immediate vs delayed).
Is food making me sick?
There are a number of potential explanations why symptoms
may worsen after eating or drinking:
Coincidence
We eat often; therefore symptoms may worsen after a meal, even
if the food is not the cause.
"Immediate allergy"
This is usually obvious, comes on very soon after exposure, and
may trigger hives, vomiting or difficulty breathing. This form
of allergy is most common in young children, is associated with
positive allergy tests, and the most common triggers are egg,
dairy, peanut, tree nuts and sometimes soy, wheat, seeds or seafood.
Delayed immune reactions to food
This is much less common, and almost always resolves by the age
of 2-3 years. Symptoms are more subtle, may start a few hours
to a few days after exposure, and allergy testing is usually negative.
The most common triggers are dairy, soy and wheat, although sometimes
other foods may be the cause. The most common symptoms are one
or more of:
o severe eczema/dermatitis,
o severe and frequent vomiting or diarrhoea,
o irritability,
o failure to put on weight, and sometimes
o blood loss from the bowel.
Unfortunately, many of these symptoms may occur in non-allergic
children, or in those with anatomical blockages in the bowel,
making it hard at times, to diagnose.
Lactose intolerance
Results in stomach/gut upset only (eg, bloating, nausea, diarrhoea),
not eczema. This is due to a partial enzyme deficiency ("lactase"),
so that lactose-containing dairy products are poorly tolerated.
Lactose-free milk causes no problems, and cheese and yoghurt are
usually better tolerated than milk. This may be a permanent inherited
condition, or can occur temporarily in a child after a bout of
gastroenteritis, in which the lining of the bowel that produces
lactase, is temporarily damaged.
How to tell the difference between lactose intolerance and cows
milk protein allergy?
In lactose intolerance, lactose-free milk will be tolerated, and
small amounts of cheese and yoghurt usually are too. When the
problem is with cows milk protein, all forms of dairy, with or
without lactose, will all cause problems.
Celiac disease
Occurs in around 1/300 people, results in inflammation of the
bowel after exposure to wheat and gluten in the diet, and may
cause one or more of diarrhoea, weight loss, poor absorption of
nutrients or fatigue and lethargy. This does involve the immune
system, but allergy testing is negative, as another arm of the
immune system is involved. It is important to note that many people
get bloated if they have too much bread or pasta, but most do
NOT have celiac disease.
Food Intolerance
Food is composed of proteins, fat, carbohydrates and other nutrients.
Most foods contain small amounts of naturally-occurring
organic molecules ("food chemicals") such as salicylates,
amines and MSG-like glutamates. Sometimes these natural "building
blocks" of food will aggravate skin or gut symptoms. Unfortunately,
allergy testing is of no use, the history is not always reliable,
and diagnosis rests on a temporary "elimination diet"
under the supervision of a skilled dietitian, followed by "challenge"
if it proves to be effective.
Food Aversion
"You just don't like it". This might be associated with
unpleasant physical or emotional reactions in the past, such as
severe food-poisoning after a certain food, followed later by
sickness in the stomach at the very thought of eating it again,
or its smell.
"Other"
There are a number of other conditions that can mimic food allergic
reactions. When these are suspected, additional tests may be required.
Principles of diagnosing food allergy
History
A suspicion is raised by the patient/parent. They are either
right or wrong. If right, then one needs to decide how food is
influencing their symptoms. One can try to confirm initial suspicions
by:
Tests
Allergy testing is only of use when food reactions
are of rapid ("immediate") onset. Negative allergy tests
do not exclude delayed immune reactions to food. In children with
severe gut symptoms, sometimes a closer examination of the bowel
may be needed. Blood tests are sometimes useful as well, particularly
when trying to assess whether the child is absorbing nutrients.
Diet manipulation
At times, it may be important to prove or disprove whether food
is causing the problem, or making it worse. This may involve temporary
dietary restrictions to remove the implicated food, followed at
times, by re-challenge.
Eczema and food allergy
Most infants with food allergy (~ 1/30 infants) have eczema
(~1/5 infants), BUT most infants with eczema do NOT have food
allergy! Food allergy does not cause eczema, but can worsen
it in some very young children. As described above, food allergy
is very common in young children in the first few years of life.
The most common causes are cows milk/dairy, soy, hen eggs, nuts,
seeds, wheat and seafood. When patients are allergic to a food,
it is usually very obvious. The majority will get intensely
itchy with large hives within an hour or less of eating. Scratching
the hives makes the eczema worse. Occasionally, babies will be
sufficiently allergic to a food to react to small amounts passing
into breast milk. The history can usually be confirmed with allergy
testing, even in very young children. Most food allergies
that aggravate eczema will disappear within the first 2-3 years
of life. Even though taking young children off wheat and milk
is often almost seen as "routine" treatment for eczema
in some quarters, it does not work in the majority. Long-term
unsupervised (and often unnecessary) dietary restriction (sometimes
advocated by alternative practitioners) can also lead to malnutrition.
Food allergy and the gut
There are many causes of vomiting and stomach upset other
than food allergy, including enzyme deficiencies, anatomical abnormalities
or non-allergic inflammatory conditions. affecting the gut. Investigation
by a stomach specialist (gastroenterologist) may also be required.
Management of food allergy
Since "desensitisation" to switch off food allergy
has not been shown to work at this time, the management of food
allergy in children involves avoidance, re-evaluation from time
to time to determine whether the allergy has resolved, education
of parents and care-givers about food allergy, sometimes deliberate
re-challenge with the food (when it is considered safe to do so),
and the development of an individual Action Plan in case accidental
exposure occurs, of particular importance where reactions are
of rapid onset and severe.
Nutritional issues
Child: infant formula is most important in the first
12-18 months of life, as a source of protein, fat, calcium and
other nutrients. As the child ages, more nutrition is obtained
from solids, leaving formula as an important source of calcium,
but not the only one. Sources of calcium include dairy products,
soy, calcium fortified rice milk, and dietary supplements. If
a child's diet needs to be restricted excessively, review by an
experienced allergy dietitian may be recommended.
Mother: where a breast-feeding mother's diet needs to be
restricted because her child is allergic to some foods, dietary
supplements may be needed. When there is evidence that a child
is allergic to many foods, it may be easier to wean a child onto
a formula and stop breast-feeding. Again, review by an experienced
allergy dietitian may be required.
Infant formulae and food allergy
Regardless of type, infant formulae are designed to be an
excellent source of nutrition. Most use cows milk or soy as the
source of protein. When children are allergic to one of more of
these, "special" formulae can be used. This might involve
substituting a soy formula in a child with cows milk allergy alone,
use of specially treated cows milk formula (such as PeptiJunior),
or use of "elemental formula" such as Neocate or Elecare,
in which there are no intact proteins for the immune system to
recognize. These may not taste as good as breast milk or even
"ordinary" formula, but perseverance, and sometimes
the use of flavours like vanilla essence or a small amount of
Golden Syrup, may make them more palatable. These formulae are
very expensive, need an Authority prescription for a PBS subsidy
in Australia, and are only approved for subsidized use in Australian
patients with combined cows milk and soy allergy under certain
conditions.
