**Skin prick test and specific IgEs in IFA**

IFA is approached initially by tests for allergen-specific IgE. The skin prick test (SPT) has a high negative predictive value (approximately 95%) and is most informative when it is negative; the positive predictive value ranges between 30% and 50% [3]. Therefore, SPT is useful for excluding IFA, but a positive result may only be suggestive of IFA. Laboratory testing for food-specific IgEs also has a high negative predictive value, estimated to be 75%, but its positive predictive value is low, ranging from 20% to 60%. Recently, the diagnostic levels of food-specific IgEs have been determined. The presence of specific IgEs at or above these levels offers a positive predictive value of approximately 95% for IFA. Although skin prick tests and serum IgE measurements can confirm sensitisation, neither of these tests can on its own prove clinical allergy to a specific food with reliability or consistency. Moreover, IgE-based laboratory tests will only predict IFA; IgE-based tests are not useful for the diagnosis of NFA in AD [18].

In spite of the extremely high specific IgE and strong SPT usually associated with HDM, HDM rarely induces anaphylactic reactions following exposure. In contrast, food-induced IgE-mediated allergies, including systemic urticaria and anaphylactic allergic reactions, can occur when a patient has high specific IgE levels or strong skin reactivity for a food allergen.

### **Interpretation of polysensitisation from the results by the SPT or allergen-specific IgE**

Polysensitisation to multiple allergens as the result of allergen-specific IgE and skin prick tests, especially to multiple food allergens, may be embarrassing to the physician. Sensitisation of the skin caused by the skin prick test and the presence of specific IgE do not indicate the presence of allergy [2].

In cases of skin sensitisation, patients often show similar reactions (itching, rash, or urticaria) to contact with allergen in the skin prick test. Therefore, patients should avoid allergens which are positive by the skin prick test. Sensitisation to specific allergens by allergen-specific IgE does not always provoke allergy. Based on the level of allergenspecific IgE, IgE-mediated allergy can be predicted, especially for food allergens. Therefore, physicians should just consider IgE-mediated food allergy if patients have high food-specific IgE.

#### **Allergy patch test**

The immunopathogenesis of eczematous allergic reactions to food that occurs in non-IgEmediated food allergy is similar to that of allergic contact dermatitis in that it is T lymphocytemediated and associated with food-specific T lymphocytes [3]. For these reasons, atopic patch testing (APT) has been used to investigate food-induced eczema.

Food Allergy in Atopic Dermatitis 237

basic recipes for each meal. For the supervision of dietary management, all food should be recorded, including elimination diets, open OFCs, and tolerance induction. This is especially important for breast-feeding infants. In such cases, the diet of the mother should be recorded along with the diet of the infant, including the times of ingestion and the time of

An elimination diet should precede an oral food challenge. Without complete elimination of the causes of the allergy provocation, it is difficult to interpret the results of an oral food

For IFA, the causative foods are typically easily recognised by parents and patients; it is therefore easy to eliminate and challenge with foods. However, it is very difficult to recognise the triggers for the diagnosis to be made in NFA. The accumulated statistics for NFA in atopic dermatitis are absolutely necessary [2]. Moreover, in cases of NFA associated with atopic dermatitis, the causative agents are more complicated and may include HDM [30]; thus, all possible allergens must be eliminated for a proper oral food challenge. Fortunately, the proper control of the causative allergens, including food and inhaled allergens, can be evaluated based on stable improvement during an elimination diet. An initial elimination diet is important as an indicator of the proper control of allergy

Once patients show improvement through an initial elimination diet, oral food challenges are conducted. Foods that were not addressed in the initial elimination diet should also be considered. IFN- therapy can be considered when patients do not improve following the initial elimination diet [2] because IFN- therapy itself does not affect allergy provocation

Without basic care and the control of allergens other than foods, the precise diagnosis of food allergies may be confusing. This type of management includes the following: 1) Skin care using non-steroid drugs and emollients including moisturizer and aroma oil, 2) House dust mite and other inhaled allergen care (dander, pollen, fungi and others); patients should be tested for allergy provocation by inhaled or environmental allergens, 3) Other factors (infection control, others), 4) Discontinue all medications that affect allergy provocation (steroids, antihistamines, other immunosuppressants, drugs with unknown effects (herbal

Diet control for the elimination of food allergy can be assessed using an elimination diet and an elementary diet. An elimination diet is a restriction of the possibly causative foods, whereas an elementary diet permits several safe foods. Both approaches require clinical data from studies [18, 19, 21]; such data are very important because if the clinical statistics are not proper, dietary restriction does not result in clinical improvement. The proper OFC then

For an effective elementary diet, the absolutely safe foods in atopic dermatitis should be addressed. An effective elimination diet is a higher modality because it requires the accumulation of clinical data for statistics regarding the causative foods for atopic dermatitis. Noh and Lee focused on these points, and an effective elimination diet is now

**4.3.2 Elimination diets as a first step in the diagnosis of food allergies** 

the appearance of new AD lesions or aggravation of old AD lesions.

2. Elimination diet

challenge [2].

provocation [2].

during the next OFC [20]. 3. Basic general management

medications), etc [2].

cannot be advanced further.

1. Elimination diet and elementary diet

available for atopic dermatitis [12, 13, 18, 19, 21].
