Approach

Diagnosis of atopic dermatitis is primarily clinical. History and physical exam are sufficient to make the diagnosis, and routine laboratory work is unnecessary. Do not use skin prick tests or blood tests, such as the radioallergosorbent test (RAST), for the routine evaluation of atopic dermatitis in the absence of a history of allergy or suspected allergy.[44]

History

Atopic dermatitis usually presents in childhood, with 45% of patients diagnosed by 6 months of age, and 70% to 85% by 5 years of age.[1][4][8]​​ Patients may have a history of other atopic conditions such as allergic rhinitis or asthma.[1]​​[35][36]

A detailed clinical and drug history should be taken, including questions such as:[45]

  • Time of onset, pattern, and severity of the atopic dermatitis

  • Response to previous and current treatment

  • Possible trigger factors (irritant and allergic)

  • The impact of the atopic dermatitis on children and their parents or caregivers

  • Dietary history including any dietary manipulations

  • Growth and development

  • Personal and family history of atopic disease.

Clinical evaluation

Skin examination to identify features associated with atopic dermatitis should be performed. Affected skin is xerotic (dry) and pruritic, but clinical presentation is variable, depending on age, disease severity, and ethnicity.[46][47][48]

Acute flares may present with dry skin with erythema and scaling, papules, or vesicles.​[48]

  • Extensor surfaces, cheeks, and forehead are preferentially affected in infants. Groin and diaper area are usually spared.

  • In older children and adults, skin flexures are most commonly affected, with hyperpigmentation or hypopigmentation and excoriations from constant scratching.

In chronic atopic dermatitis, the skin appears thick and lichenified. Other presentations in adults include head and neck dermatitis, hand dermatitis, or prurigo lesions.[47] Follicular hyperkeratotic papules known as keratosis pilaris (KP) may be present on the extensor surfaces of the upper arms, buttocks, and anterior thighs, and are typically asymptomatic.[48] KP are often seen in patients with atopic dermatitis, but may also be present in the absence of atopic dermatitis.[Figure caption and citation for the preceding image starts]: Hypopigmentation on the dorsal aspect of the hand in a 12-year-old girl with atopic dermatitisFrom the personal collection of A. Hebert, MD; used with permission [Citation ends].com.bmj.content.model.Caption@65c1e7e2[Figure caption and citation for the preceding image starts]: Papules, lichenification, and hypopigmentation in a child with chronic atopic dermatitisFrom the personal collection of A. Hebert, MD; used with permission [Citation ends].com.bmj.content.model.Caption@141edc30[Figure caption and citation for the preceding image starts]: Hypopigmentation on the flexural skin of the ankles in the same patientFrom the personal collection of A. Hebert, MD; used with permission [Citation ends].com.bmj.content.model.Caption@2b3d2ebc

Overlap between acute and chronic atopic dermatitis may be seen due to the recurrent nature of the disease.[45][48]

The presentation of atopic dermatitis is considered to be similar amongst ethnic groups. Nuances in the visual appearance of atopic dermatitis can occur due to differences in pigmentation and distribution of lesions. For example:[45][46]

  • More well-demarcated lesions and increased scaling and lichenification are more common in Asian patients

  • Patients of African descent are less likely to develop flexural dermatitis, but rather present with extensor involvement as a more prominent feature

  • Discoid or follicular patterns may be more common in Asian, black Caribbean, and black African children.

Consideration of coexistent allergy

There is no pathognomonic marker for the diagnosis of atopic dermatitis. Food allergy can contribute to disease exacerbation in 30% of children with atopic dermatitis, with foods such as egg or cows' milk commonly implicated.[49] Pollen‐associated food allergy can occur in all ages.[50]​​​

When to consider food allergy testing

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]

Peripheral immunoglobulin E (IgE) levels or skin-prick testing

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]​ Do not perform any unproven diagnostic tests, such as immunoglobulin G (lgG) testing.​[51][56]​​

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]

The risks and benefits of food testing should be discussed with the patient and their family.

Inhalant allergy

Airborne allergens (including pollen and malassezia yeast) can flare atopic dermatitis and usually present with exacerbations of disease on the head and neck.[50]​​

In the UK, a diagnosis of inhalant allergy should be considered in children:[45]

  • with seasonal flares of atopic dermatitis

  • with atopic dermatitis associated with asthma or allergic rhinitis

  • ages 3 years or over with atopic dermatitis on the face, particularly around the eyes.

Patch testing

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]

Allergic contact dermatitis may have a more precipitous onset than atopic dermatitis, and be patchy and irregular in distribution and border. 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] Contact allergy to ingredients in topical therapeutics is known to be increased in people with atopic dermatitis.[61]

The discovery of an allergen or allergens in an atopic child or adult may alleviate further burden of disease and allow better overall responsiveness to appropriate therapy.[62] Treatment of allergic contact dermatitis includes removal of the offending agent and education regarding future avoidance of the contactant.

Skin biopsy

May be considered to differentiate atopic dermatitis from allergic contact dermatitis, and also from mycosis fungoides or psoriasis.[63]​ 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.

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