Tests
1st tests to order
clinical diagnosis
Test
Usually no tests are necessary.
Result
features of atopic dermatitis; xerosis, hyperlinear palms, inflammatory papules, lichenification
Investigations to avoid
IgG testing
Recommendations
Do not perform lgG tests in the evaluation of co-existing food allergy.[56]
Rationale
IgG testing is unproven and can lead to inappropriate diagnosis and treatment. Appropriate diagnosis of allergy requires specific IgE testing in a patient with a relevant medical history.[56] However, IgE testing is not routinely performed for atopic dermatitis if the diagnosis is clear on grounds of history and exam.[63]
radioallergosorbent test
Tests to consider
IgE levels
Test
Not routinely performed if diagnosis is clear on grounds of history and exam.[63]
Testing for food allergy in patients with atopic dermatitis should not be considered before intervention with patient education and optimal skin care, including topical corticosteroids, has been initiated.[51]
In the UK, a diagnosis of food allergy should be considered in children with atopic dermatitis who have reacted to a food with immediate symptoms, or in infants and young children with moderate or severe atopic dermatitis that is not controlled by optimal management, particularly if associated with gut dysmotility, or with failure to thrive.[45]
High sensitivity and low specificity of skin-prick and IgE testing for food allergy can yield false positive results, which may lead to elimination diets that are potentially harmful to patients with atopic dermatitis.[51] Effects such as progression to immediate-type allergy, including anaphylactic reactions, have been reported.[51][52][53][54]
Therefore, skin-prick or IgE testing should only be considered for patients who have a history of allergy to food (e.g., exacerbation of atopic dermatitis after consumption of egg).[51][54][55]
Special consideration should be given to infants with severe atopic dermatitis, egg allergy, or both, as they have the highest a priori risk for developing peanut allergy.[57] An IgE or skin-prick test is strongly recommended before introducing peanuts into their diet.[51]
Result
elevated IgE blood levels
skin-prick testing
Test
Not routinely performed if diagnosis is clear on grounds of history and exam.[63]
Testing for food allergy in patients with atopic dermatitis should not be considered before intervention with patient education and optimal skin care, including topical corticosteroids, has been initiated.[51]
In the UK, a diagnosis of food allergy should be considered in children with atopic dermatitis who have reacted to a food with immediate symptoms, or in infants and young children with moderate or severe atopic dermatitis that is not controlled by optimal management, particularly if associated with gut dysmotility, or with failure to thrive.[45]
High sensitivity and low specificity of skin-prick and IgE testing for food allergy can yield false positive results, which may lead to elimination diets that are potentially harmful to patients with atopic dermatitis.[51] Effects such as progression to immediate-type allergy, including anaphylactic reactions, have been reported.[51][52][53][54]
Therefore, skin-prick or IgE testing should only be considered for patients who have a history of allergy to food (e.g., exacerbation of atopic dermatitis after consumption of egg).[51][54][55]
Special consideration should be given to infants with severe atopic dermatitis, egg allergy, or both, as they have the highest a priori risk for developing peanut allergy.[57] An IgE or skin-prick test is strongly recommended before introducing peanuts into their diet.[51]
Reactions are assessed by the degree of redness and swelling and the size of the weal produced.
Result
reactivity to allergen
oral food challenge
Test
Testing for food allergy in patients with atopic dermatitis should not be considered before intervention with patient education and optimal skin care, including topical corticosteroids, has been initiated.[51] Patients under 5 years old with moderate to severe atopic dermatitis, who are unresponsive to initial treatment, should be tested for food allergy using oral food challenge or trial elimination diet.[51]
In the UK, a diagnosis of food allergy should be considered in children with atopic dermatitis who have reacted to a food with immediate symptoms, or in infants and young children with moderate or severe atopic dermatitis that is not controlled by optimal management, particularly if associated with gut dysmotility, or with failure to thrive.[45]
Result
exacerbation of atopic dermatitis symptoms after oral food challenge
trial elimination diet
Test
Testing for food allergy in patients with atopic dermatitis should not be considered before intervention with patient education and optimal skin care, including topical corticosteroids, has been initiated.[51] Patients under 5 years old with moderate to severe atopic dermatitis, who are unresponsive to initial treatment, should be tested for food allergy using oral food challenge or trial elimination diet.[51]
In the UK, a diagnosis of food allergy should be considered in children with atopic dermatitis who have reacted to a food with immediate symptoms, or in infants and young children with moderate or severe atopic dermatitis that is not controlled by optimal management, particularly if associated with gut dysmotility, or with failure to thrive.[45]
Result
improvement in atopic dermatitis symptoms after trial elimination diet
patch testing
Test
Allergic contact dermatitis may complicate the clinical course of atopic dermatitis. Patch testing should be considered for any child or adult whose dermatitis remains difficult to control or presents in a specific location suggestive of an external trigger.[58][59][60]
Diagnosis is by patch testing, whereby suspected allergens are placed on unaffected skin of the back for a period of 48 hours. Irritant reactions are evaluated when the patch is removed, and again at subsequent follow-up appointments for delayed reactions.
Common contact allergens in patients with atopic dermatitis include, but are not limited to, nickel, neomycin, fragrance, formaldehyde, and rubber chemicals.[55]
Result
reactivity to allergen
skin biopsy
Test
May be considered to differentiate atopic dermatitis from allergic contact dermatitis, and also from mycosis fungoides or psoriasis.[63][65]
Used less frequently than skin exam, which considers primary lesions, their distribution, the associated symptomatology, and the skin disease's duration and associations at the time of onset.
Result
findings consistent with atopic dermatitis including spongiosis acanthosis, and chronic inflammatory infiltrate, mainly composed of lymphocytes, mast cells, and eosinophils
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