Food-induced contact urticaria syndrome (CUS) in atopic dermatitis: reproducibility of repeated and duplicate testing with a skin provocation test, the skin application food test (SAFT)

The many faces of pediatric urticaria

Urticaria is a common disease that can affect individuals of all age groups, with approximately one-quarter of the population experiencing it at least once in their lifetime. Lesions characterized by erythema and itchy hives can appear anywhere on the body. These can vary in size ranging from millimeters to centimeters, and typically clear within 24 h. About 40% of patients with urticaria have accompanying angioedema, which involves localized deep tissue swelling. Urticaria usually occurs spontaneously and is classified into acute and chronic forms, with the latter referring to a condition that lasts for more than 6 weeks. The prevalence of chronic urticaria in the general population ranges from 0.5% to 5%, and it can either be inducible or spontaneous. The most common form of pediatric urticaria is acute and is usually self-limiting. However, a broad differential diagnosis should be considered in children with urticaria, particularly if they also have accompanying systemic complaints. Differential diagnoses of pediatric urticaria include chronic spontaneous urticaria, chronic inducible urticaria, serum sickness-like reaction, urticarial vasculitis, and mast cell disorders. Conditions that can mimic urticaria, including but not limited to cryopyrinopathies, hyper IgD syndrome, Periodic Fever, Aphthous Stomatitis, Pharyngitis and Adenitis (PFAPA), Tumor Necrosis Factor Receptor Associated Periodic Syndrome (TRAPs), and Schnitzler syndrome should also be considered. The many faces of pediatric urticaria can be both easy and confusing. A pragmatic approach relies on clinical foresight and understanding the various forms of urticaria and their potential mimickers. This approach can pave the way for an accurate and optimized diagnostic approach in children with urticaria.

The significance of allergic contact urticaria to milk in children with cow's milk allergy

BACKGROUND

Cow's milk allergy (CMA) is the most common food allergy in infancy. Food allergy is generally triggered through ingestion, but can also be triggered through skin contact. We investigated the incidence and the clinical significance of cow's milk protein (CMP)-induced contact urticaria in individuals with CMA with and without atopic dermatitis (AD).

METHODS

A total of 157 children of whom 133 were diagnosed with CMA were participated. The study was based on observational data gathered in the course of patient care, including a skin prick test and a 'finger test', in which cow's milk is applied on the cheek by a physician's finger to detect contact urticaria.

RESULTS

Eighty nine of 133 patients (66.9%) had IgE-mediated CMA. Forty of these 89 (44.9%) tested positive in the finger test. Family atopy was higher in those with positive contact urticaria [21/40 (52.5%) vs. 14/49 (28.5%), p = 0.029]. Patients with positive vs. negative CMP contact urticaria had higher incidence of multiple food allergies [20 of 40 (50%) vs. 7/49 (14.3%), p < 0.004]. IgE-mediated CMA patients with AD had statistically higher CMP allergic contact urticaria compared to patients without AD [71% (15/21) vs. 37% (25/68), p = 0.0064]. Children with non-IgE milk allergy and healthy control group did not have contact urticaria to CMP.

CONCLUSION

CMP contact urticaria exists only in patients with IgE-mediated CMA. A 'finger test' to CMP should be part of the evaluation of CMA patients, and positivity suggests the potential for multiple food allergies, especially to sesame and egg.

Delayed- and immediate-type reactions in the atopy patch test with food allergens in young children with atopic dermatitis

In recent years, the atopy patch test (APT) has been suggested as an addition in the allergological work-up of children with atopic dermatitis (AD) and suspected food allergy. We initiated a prospective clinical study in children with AD younger than 3 yr, to evaluate the additional clinical value of the APT next to our own standardized allergological work-up in case of a suspected food allergy. One hundred and thirty-five children were included in the study. They were tested using the skin application food test (SAFT), the APT and measurement of specific IgE. The allergens used in the skin tests were freshly prepared food stuffs and included commercially available cow's milk (CM), the egg white of a hard boiled hen's egg and mashed peanuts in a saline solution. Allergy was defined using a flowchart incorporating the results from the SAFT, oral challenges (OCs) and elimination and (re)introduction periods. To determine the additional value of the APT next to the SAFT, we analyzed the SAFT negative patients per allergen and used an exact binary logistic analysis to evaluate the simultaneous effects of the APT and measurement of specific IgE, calculating mutually adjusted odds ratios (ORs) for positive APTs and specific IgE levels above 0.70 U/l. We found clinically relevant food allergies in 23% (egg white) to 28% (CM and peanut) of our study population. Positive SAFT reactions were observed in 14% (peanut), 16% (egg white) and 21% (CM) of our patient population. Next to the SAFT, we did not observe a significant additional value of the APT for the diagnosis of CM or egg white allergy, but we did find a significant additional value for the diagnosis of peanut allergy (OR = 11.56; p < 0.005, 2-sided). In clinical practice this statistically significant value does not exclude the need for OC and controlled elimination and (re)introduction periods due to the presence of false-negative as well as false-positive results in the APT. In conclusion, we could not find enough support for the current addition of the APT to our standardized allergological work-up in young children below the age of 3 yr with AD and suspected food allergy. At the moment the additional value of the classical delayed-type APT next to the SAFT seems to be very limited at best in this study population and does not justify the time-consuming nature of the skin test.

Frequency and significance of immediate contact reactions to peanut in peanut-sensitive children

BACKGROUND

Parents of atopic children frequently report, and are alarmed by, contact reactions to foods. Some schools restrict foods due to concerns regarding possible systemic reactions following contact in allergic children.

OBJECTIVE

We aimed to determine the frequency with which peanut-sensitive children exhibited contact sensitivity to peanut butter and to assess the significance of such reactions.

METHODS

One gram of peanut butter was applied directly to the skin of 281 children who were skin prick test (SPT) positive to peanut (immediate skin application food test; I-SAFT). The test was considered positive if one or more weals were present when the patch was removed after 15 min. A subset of children then underwent an open-label oral challenge with graded amounts of peanut protein.

RESULTS

During 3515 clinic visits, 330 I-SAFT tests for peanut contact sensitivity were performed; 136 (41%) were positive. The mean SPT diameter was 10 mm in the I-SAFT-positive children and 8.5 mm in the I-SAFT-negative children (t-test, P<0.0001). No child had a systemic reaction following topical application of peanut butter. Eighty-four children had 85 oral challenges after blinded, placebo-controlled I-SAFT testing. Challenge was positive in 26/32 of those with a positive I-SAFT and negative in only 6/32. Challenge was also positive in 26/53 but negative in 27/53 of those with a negative I-SAFT (sensitivity 50%, specificity 82%, chi2, P=0.003).

CONCLUSION

A minority of children sensitized to peanut (positive SPT) develop localized urticaria from prolonged skin contact with peanut butter. No tested subjects, including ones with systemic reactions upon oral challenge, developed a systemic reaction to prolonged skin exposure to peanut. Therefore, systemic reactions resulting from this mode of contact with peanut butter appear highly unlikely.

Combining skin prick, immediate skin application and specific-IgE testing in the diagnosis of peanut allergy in children

Previous studies have suggested various diagnostic cut-offs of allergy tests for the diagnosis of clinical peanut allergy in children. There are few data relating to the use of combinations of these tests in children. We aimed to determine the validity of previously reported diagnostic cut-off levels of peanut allergen skin tests and peanut specific-immunoglobulin (Ig) E, as well as the usefulness of combinations of these, for predicting clinical peanut allergy in our Allergy Clinic. Children attending the Allergy Clinic with a positive peanut skin prick test (SPT; n = 84) were included in the study. Immediate skin application food tests (I-SAFT) using 1 g of peanut butter (positive if any wheals were detected at 15 min), peanut specific-IgE levels and open-label peanut food challenges were performed. Fifty-two of 85 peanut challenges were positive. Skin prick test specificity was 67% at >or=8 mm and 100% at >or=15 mm. The I-SAFT was 82% specific. A peanut specific-IgE level of 0.37 kU/l was 98% sensitive but 33% specific. A level of 10 kU/l was 100% specific. Combinations of a SPT of >or=8 mm with a positive I-SAFT and a peanut specific-IgE >or=0.37 kU/l were 88% specific with a sensitivity of 38%. Using challenge outcomes as the standard, available in vitro and in vivo diagnostic tests for peanut allergy have poor sensitivity and specificity and combining them does not significantly improve their clinical usefulness. Previously described diagnostic cut-off levels do not have general applicability. Allergy practitioners may need to interpret results of allergy tests in the context of their own practices.

Proceedings of the 4th Georg Rajka International Symposium on Atopic Dermatitis, Arcachon, France, September 15-17, 2005

The 4th Georg Rajka International Symposium on Atopic Dermatitis presented a comprehensive view of our current understanding and management of atopic dermatitis (AD). These proceedings highlight contributions related to the history of AD doctrines; genetic and epigenetic background; epidemiology; maturation of the immune system; infection and innate-adaptive immunity; epidermal inflammation, including neurogenic inflammation and pruritus; animal models; skin barrier; evidence-based therapy and education programs; prognostic and severity markers; and allergy testing. Several studies in animal models and human subjects point to impaired skin barrier function as a primary defect that facilitates the effect of environmental factors and immune dysregulation found in AD. The new frontier in AD therapy should, in the near future, reflect our better understanding of the skin barrier. The influence of environmental factors on the skin and other epithelial barriers in the perinatal period needs to be better understood to implement appropriate prevention programs.

An evaluation of the diagnostic value of different skin tests with egg in clinically egg-allergic children having atopic dermatitis

Skin testing is a common diagnostic procedure in food allergy, but the final diagnosis of food allergy is based on the clinical response to food challenge. We studied the value of the skin prick-prick test (SPT), skin application food test (SAFT) and atopy patch test (APT) with fresh egg extract in diagnosing egg allergy. Ten clinically egg-allergic children with atopic dermatitis (AD; age 10 months to 8.4 yr, mean 3.4 yr) and 10 egg-tolerant children with and 10 without AD (age 2.4-11 yr, mean 5.5 yr) participated. In SAFT several false-negative reactions were seen, whereas all clinically egg-allergic children were positive in SPT and 40-60% in APT. In APT and in SPT false-positive reactions to egg were observed. In this study comprising a small number of patients including control subjects, neither SAFT nor APT with fresh whole egg extract were able to increase the diagnostic accuracy in detecting egg-allergic children with AD compared with SPT.

IL-13 is necessary, not simply sufficient, for epicutaneously induced Th2 responses to soluble protein antigen

Th2 responses are clearly involved in the pathogenesis of atopic disease. Thus, understanding the factors responsible for Th2 sensitization at sites of allergen exposure, such as airway and skin, is crucial for directing therapeutic or preventive strategies. Contrary to other models of Th2 sensitization to proteins, we have reported that Th2 responses induced by epicutaneous exposure to OVA are IL-4 independent. Combined deficiency of both IL-4 and IL-13 signaling did prevent Th2 generation, suggesting that IL-13 was mediating these IL-4-independent responses. It was not clear, however, whether IL-13 was simply replacing the need for IL-4 in genetically deficient mice or if IL-13 played a unique role. In the present study, we show that Th2 responses induced by epicutaneous OVA exposure (including lung inflammatory responses after inhaled Ag challenge, OVA-specific IgG1, and draining lymph node IL-5 production) are impaired in IL-13-deficient (IL-13(-/-)) mice compared with wild type. In contrast, i.p. sensitization of IL-13(-/-) mice resulted in responses equivalent to wild type. Generation of contact hypersensitivity to dinitrofluorobenzene, which involves Th1 and CD8(+) effector cells, was also intact in IL-13(-/-) mice. Taken together, the data indicate that IL-13 is the major inducer of Th2 generation in the cutaneous microenvironment, being required independently of IL-4. This fact, in combination with the known abundance of IL-13 in atopic dermatitis skin lesions, emphasizes the potentially important role of the skin as a site for Th2 sensitization to environmental allergens, particularly in atopic individuals.

Markers for early sensitization and inflammation in relation to clinical manifestations of atopic disease up to 2 years of age in 133 high-risk children

BACKGROUND

The combination of genetic susceptibility and environmental factors induce allergic sensitization and subsequently local inflammation, resulting in atopic manifestations.

OBJECTIVE

To examine whether immunological features reflecting sensitization (total and specific IgE levels, allergen-induced proliferative responses and skin tests) and markers of inflammation (plasma sE-selectin and blood eosinophils) are related to the clinical expression of atopy and whether they precede atopic disease in children up to 2 years of age.

METHODS

The development of these markers during the first 2 years of life was studied prospectively in 133 newborns at high risk to develop atopic disease.

RESULTS

The prevalence of atopic disease increased from 25% at 12 months to 32% at 24 months of age. The children with food allergy at 12 months, who all had atopic dermatitis (AD), turned out to have asthma-like disease in 40% and AD in 100% at the age of 24 months. Total IgE levels increased with time and from 12 months onward levels started to differ markedly between atopics and nonatopics. Food-specific IgE antibodies were significantly associated with AD (relative risk [RR] = 2.39), food (RR = 1.32) and upper-airway allergy (RR = 1.20), and house dust mite-specific IgE antibodies with upper-airway allergy (RR = 5.00). A positive skin test was significantly associated with AD (RR = 2.90) and food allergy (RR = 1.36). The inflammation markers investigated, were not related to the clinical expression or preceded atopic disease at 2 years of age in high-risk children.

CONCLUSION

Positive skin tests and specific IgE to food or inhalant allergens were related to the clinical expression of different atopic diseases. The combination of AD and food allergy at 12 months reflected the strongest risk factor in this high risk cohort for the development of asthma-like disease at 24 months of age.

Diagnostic tests in children with atopic dermatitis and food allergy

BACKGROUND

Skin testing is a common diagnostic procedure in food allergy. The skin prick test is the test of first choice for investigating the immediate IgE-mediated reaction. The skin application food test (SAFT) has been developed on the basis of the mechanism of the contact urticaria syndrome (CUS).

METHODS

We studied the relevance of the SAFT in children younger than 4 years with atopic dermatitis and (suspected) food allergy as compared with the prick-prick test, the radioallergosorbent test (RAST), and the oral challenge. In the skin tests, we used fresh food, in the same state as it was consumed.

RESULTS

There was a good agreement between the SAFT and the prick-prick test. A moderate agreement was observed between the SAFT and the serologic test (RAST). Significantly more positive results in the RAST were observed than in the SAFT. There was very good agreement between the SAFT and the oral challenge (kappa = 0.86).

CONCLUSIONS

The SAFT is a reliable and child-friendly skin test for evaluating (suspected) food allergy in children younger than 4 years with atopic dermatitis. The very good correlation with the oral challenge indicates that one may probably consider the SAFT a "skin provocation" in children younger than 4 years.

Allergy skin tests for inhalants and foods. Comparison of methods in common use

Many types of skin tests have evolved from Blackley's early scratch tests. This review highlights both the similarities between current skin tests and their differences. All current skin tests are capable of detecting allergic hypersensitivity, but the tests differ in their sensitivity, specificity, safety, reproducibility, and applications. Common factors in initial and final test doses, and in test dose increments, are identified. Test methods that quantitatively measure a range of allergen concentrations have diagnostic advantages in terms of safely detecting a wide range of allergic sensitivities. Failure to detect the full spectrum of allergic disease can lead to treatment failure; therefore, complete skin testing is desirable. This is especially important when dealing with exquisitely sensitive patients, such as many grass or ragweed sensitized patients, but is equally vital when evaluating low sensitivity patients, including many who are mold or food sensitive. Quantitation also improves test reproducibility, which is why it is used for antigen standardization. Finally, quantitation has advantages when used to initiate and escalate allergen immunotherapy. In vivo testing continues to evolve. New types of prick testing devices, and refinements of intradermal and patch test methods, continue to be reported. All allergists need to stay current with developments in vivo testing, so that they can offer their patients diagnosis that is appropriate to each individual situation.