57 Dietary Management of Atopic Eczema
C. Kugler
57.1 Definitions
Adverse reactions to food are a topic that has increased in importance over the last few years. In addition to toxic reactions, such as mushroom poisoning or aller- gy-like reactions caused by histamine (e.g., fish poi- soning), these clinical pictures are differentiated as to whether food hypersensitivity or food intolerances are involved [25].
Food allergies are based on immunological mecha- nisms, which cause patients to form allergen-specific antibodies (e.g., against cow’s milk protein), most fre- quently triggered by the immediate-type, immuno- globulin-mediated reaction [19].
All other nonimmunologically triggered reactions are assigned to food intolerances [5]. These include:
1. Metabolic reaction due to an enzyme deficiency 2. Pharmacological mechanisms
3. Unknown mechanisms (food idiosyncrasy).
Lactose intolerance is the most frequently occurring among the enzymatic intolerances.
Pharmacological intolerances are shown by patients after consuming foods that have a high content of bio- genic amines or of histamine-releasing substances.
Food additives such as flavor enhancers or preserva- tives (sulfites) used on foods may cause a food intoler- ance in some people. The symptoms of food intoler- ance vary and can be mistaken for those of a food aller- gy, i.e., they may cause a worsening of eczema in cases of patients suffering from atopic eczema. Major trig- gers are food additives: preservatives, coloring agents, antioxidants, and naturally occurring ingredients [10].
Food may trigger and sustain an atopic eczema. The symptoms of an early reaction usually occur within a few minutes to 2 h [19]. Late reactions involving a dete-
rioration of the skin may be observed up to 48 h after consuming the food. In addition to deterioration of the atopic eczema, simultaneous manifestations may also occur in other systems such as in the gastrointestinal tract and the respiratory tract.
57.2
Prevalence of Adverse Reaction to Food in Atopic Eczema
Although food allergy is often presumed, it affects far fewer patients with atopic eczema than generally assumed. About 30 % of children with atopic eczema may have food allergy. In adults, the figure is somewhat lower. [17]. The prevalence of food allergy is correlated with the severity of the atopic eczema: whereas there are very few food allergies to be found in the case of localized atopic eczema, the frequency increases in patients with moderate and severe atopic eczema [14].
In the United States, six food allergens (hen’s eggs, cow’s milk, peanut, soya, fish, and wheat) are responsi- ble for more than 90 % of the test reactions [29]. Aller- gies to food in terms of cross-reactions to pollen are rarer in childhood but more common in adults. Typi- cal examples of cross-reactivity between foods and pollen are apple, birch, celery, mugwort, hazelnut, and birch pollen [26]. Adverse reactions to food occur rarely.
57.3 Diagnosis
The diagnostic system for adverse reactions to food comprises several steps. There is no laboratory test that provides proof [21, 27]. The diagnosis is sometimes Chapter57
very simple if an exacerbation of the skin can be repeat- edly associated over time with a food and allergy tests support this finding. However, diagnosis is frequently difficult and time-consuming, in particular if late reac- tions do not provide a clear pointer to a food or if adverse reactions to food are involved for which no lab- oratory test provides clear information. For this rea- son, it is necessary to undertake a step-by-step proce- dure that is geared to the patient in question [19].
The first and most important step in allergological diagnosis is taking the history. A clear case history may make further steps unnecessary [33]. If there are symp- toms that are difficult to interpret, further diagnostic procedures may be planned after an exact history [4, 5, 30].
In addition to the history, patients should keep a diet diary. On occasions, the symptoms can be assigned to a particular food. The interpretation of the records is, however, difficult because of undeclared
“hidden” food allergens [22]. Also, foods that are assumed by patients (or parents) are more heavily emphasized.
The in vitro diagnostic system is conducted with the demonstration of specific immunoglobulin in serum (RAST). In the case of a nonspecific suspicion, the allergens that are the most frequent for the age are test- ed. A high specific IgE demonstrates a sensitization to a food, but does not allow any conclusions to be drawn as to a relevant allergy. As with RAST, a positive result in the skin prick test has the function of being only a pointer to the subsequent oral challenge. It is by no means an indication for a therapeutic diet [20].
57.4
Diagnostic Types of Diet
57.4.1
Elimination Diets
If there is a specific suspicion that one or more foods trigger an allergy for a patient, a so-called specific elimination diet (e.g., avoiding cow’s milk) is carried out. Babies are given a compatible formula, e.g., ex- tensively hydrolysed formula (Nutramigen, Pregesti- mil, Alfar´e) or a formula made of an amino acid mix- ture (Neocate, Pregomin AS). Allergic symptoms have also been reported after hydrolysed protein prepara- tions, extending as far as anaphylactic reactions [6, 23, 28].
Example of an oligoallergenic diet Cereals: Rice
Meat: Lamb, turkey
Vegetables: Cauliflower, broccoli, zucchini Fruits: Pear, banana
Fat: Sunflower oil, none-milk margarine Drinks: Mineral water, tea
Condiments: Salt, sugar
If there is no improvement in the eczema while follow- ing the elimination diet, an adverse reaction to food appears to be improbable as a challenging factor. If there is an improvement in the symptoms, a food chal- lenge follows with the suspected food, under medical supervision.
In the case of a nonspecific suspicion, an oligoanti- genic diet can be followed, using those foods that rarely trigger allergies in the corresponding age group and that are not conspicuous in the history. The diet com- prises approximately 15 foods that are not suspected of triggering allergies in the case of the patient. The diet is put together individually for each patient and carried out for at least 10 days. There is then a food challenge or a follow-up diet. The elimination diet comprises an oligoantigenic diet for older children, adolescents, and adults with nonspecific suspicion of a food allergy.
In the case of babies who are being breast-fed, the mother (depending on the suspected and challenged food) should follow a corresponding elimination diet before and during the oral challenge tests, since in rare cases there may be a transfer of allergens to the child via the mother’s milk when the mother is taking food rich in allergens [30], thus falsifying the result of the challenge.
An improvement in the complaints following the elimination diet may be merely a pointer to the clinical relevance of the suspected trigger. Only a subsequent challenge provides the necessary confirmation.
If the symptoms improve after the oligoantigenic diet, foods are systematically added every 2 or 3 days until the diet again corresponds to a “normal” diet and until all foods have been identified that trigger the adverse reaction.
57.4.2
Food Challenges 57.4.2.1
Double-Blind Placebo-Controlled Oral Food Challenge The gold standard in food allergy diagnosis is the dou- ble-blind placebo-controlled food challenge (DBPCFC) [1, 3, 4, 18, 31]. The oral challenge is intended either to prove a food allergy so as to eliminate the food in ques- tion for a certain time or to show that foods are not a challenging factor for the atopic eczema and unneces- sary dietetic restrictions can be lifted.
Patients who have reactions to foods that can be des- ignated with certainty as anaphylactic are usually not subjected to challenge testing [4].
Particularly in the case of time-delayed reactions, it is difficult to decide whether there is a connection between the consumption of a food and the symptoms.
The DBPCFC guarantees a more objective diagnosis.
Resolution comes in 48 h, after the doctor has deter- mined whether the patient has reacted or not.
An exacerbation in the skin finding is evaluated using a standardized evaluation sheet, e.g., the SCO- RAD [12].
Double-blind placebo-controlled challenge foods may be administered, for example, in extensively hydrolysed formula. The challenging food may also be pur´eed with compatible mashed foods (e.g., mashed potato) or stirred into pudding (soy pudding). A pro- tein-free mash based on carob bean flour and rice has proven its worth. The foods are masked as required with q -carotene, beet, currant, or carrot juice (if aller- gologically possible). To match the flavor, a flavoring agent (orange) is added, sweetened with sugar, or thick pear juice.
Because of the feared early reactions, oral challenges should be carried out by titration (increasing the quan- tity every 30 min), beginning, for example, with 0.2 ml.
The total challenge dose should correspond to about an average daily consumption (e.g., 1 hen’s egg, 150 ml milk) [9].
57.4.2.2
Challenges in the Case of an Adverse Reaction to Food In the case of a suspicion of an adverse reaction to food that is not based on immunological mechanisms and, for this reason, no antibodies are formed, there is no possibility of obtaining pointers to the triggers by
using skin or blood tests. Diagnostic diets are unavoid- able in these cases. Allergy clinics usually work togeth- er with nutritional specialists who have experience in this field. Such nutritional specialists are able to pro- vide patients with individual counseling and to com- pile the diet before such a drastic diet is followed. The pseudoallergen-poor diet [34] (without additives, avoiding biogenic amines, and naturally occurring salicylic acid) is carried out over a period of approxi- mately 4 weeks and is then tested under inpatient con- ditions with a pseudoallergen-rich diet over at least 2 days. In the case of this challenge, it is important that as high as possible doses of the suspected food or addi- tives are administered since the reactions are dose- dependent. If a patient reacts during the challenge, the procedure is stopped. The test substances are packaged and administered individually and in capsules so the ingredients that have caused the reaction in the high- pseudoallergenic diet are known.
57.4.2.3
Challenges in the Case of a Suspicion of Cross-Reaction to Pollen
Patients who have a pollen allergy also react to food in a number of cases, since there are cross-reactive struc- tures in both sources of allergens. The oral allergy syn- drome frequently occurs with oropharyngeal symp- toms, but there are also patients with eczema (fre- quently late reactions) and urticaria. The allergens are in many cases unstable and react to heat, i.e., some pro- cessed products may be tolerated or the symptoms do not occur so forcefully. This necessitates a particularly careful procedure in taking the history as well as in the challenge. In the case of the subsequent challenge, all products that contain pollen-associated food are avoided over a certain period of time. The challenge is then made with the suspected products.
Pollen-associated food allergies within the meaning of an oral allergy syndrome (OAS) [24] can mostly be diagnosed on the basis of clinical experience in con- junction with the corresponding sensitization patterns and do not necessarily require oral challenges.
536 57 Dietary Management of Atopic Eczema
57.5
Nutritional Recommendations When There Is a Food Allergy
If a food allergy has been diagnosed, treatment consists in an individually adapted elimination diet. This should involve substitution of the ingredients that can- not be properly provided on the basis of the elimina- tion (e.g., calcium in the case of a cow’s milk allergy).
Counseling provided by a dietitian who is trained in the allergological field is essential for implementing the medically prescribed diet. In addition to informa- tion on avoiding proven allergens and the production of suitable meals, factors that are important for the patient’s quality of life should also be taken into account: security by way of consistently avoiding the trigger or triggers and proper nutrition are the basic elements for good disease management. However, the patient’s perceived quality of life will also depend to a large extent on whether he or she is being offered acceptable alternatives for the eliminated food [9].
Elimination of food without a secure diagnostic sys- tem is not reasonable for the patient. There are several case reports of major side effects resulting from strict, one-sided diets [8, 13, 15]. The period of consistently avoiding the noncompatible food should be 1 year for children [19]. Thereafter, there must be retesting to evaluate the current clinical status.
The moste common food allergens are found in a wide variety of processed foods [16, 22]. In Europe the use of these foods is nowadays possible since a new directive from the European Parliament and of the Council is in practice.
Twelve groups of food independent of the concen- tration of allergens must be labelled since November 2004. Member states of the EU shall bring into force, by 25 November 2004 the laws, regulation and administra- tive provisions necessary to: Permit, as 25 November 2005, the sale of products that comply with the direc- tive; and prohibit, as from 25 November 2005, the sale of products that do not comply with this directive. Any products which do not comply with this directive but which have been placed on the market or labelled prior to this date may, however, be sold while stocks last.
These twelve groups of food are cereals containing gluten, crustaceans, eggs, fish, peanuts, soybeans, milk (including lactose), nuts, celery, mustard and sesame seeds as well as their products and sulphur dioxide and sulphites at concentration of more than 10 mg/kg or
10 mg/l. In addition, the regulation also applies to alco- holic drinks if they contain one of the above-men- tioned ingredients or allergens. There also continues to be no obligation to label ingredients in very small quantities (e 2 %) so as to avoid extremely long “lists of ingredients” and thus avoid overregulation. This toler- ance limit does not apply, however, to allergens which are included in the list [7, 11, 32].
Contamination (cross contact) may develop as a result of producing various composite food on the same production lines. This contamination cannot always be excluded in spite of special cleaning processes. The pro- ducers safeguard themselves by noting that the product
“may contain traces of nuts,” for example. However, this indication should be an exception and not, as the case today, printed on all products to provide a safeguard against consumers’ liability claims [32].
57.6
Prognosis for Food Allergies
Studies have demonstrated the disappearance of food allergy symptoms in up to one-third of children and adults in 1 – 3 years, although positive skin tests and positive serum IgE levels may persist. This is why there is the demand that clinical relevance be checked at reg- ular intervals. Since there is no reliable laboratory test for the prognosis, the oral challenge must be repeated after 12 – 24 months. Evidence suggests that the proba- bility of outgrowing a food allergy depends upon the food allergen and the patient’s compliance with the elimination diet. Allergies to peanut, nuts, fish, and other seafood appear to be more persistent.
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538 57 Dietary Management of Atopic Eczema
