If you think you or your kid has school sores you should see your docotor. A impetigo diagnosis is usually straightforward from the typical look of the skin infection.

Sometimes school sores can be confused with other skin conditions such as shingles, fungal skin infections or cold sores. If there is any doubt, your doctor might take a swab from the affected area. The swab will be tested for impetigo at a laboratory.

Doctors usually diagnose impetigo by considering signs and symptoms and medical history and looking at the distinctive sores. Your doctor will likely ask about any recent cuts, scrapes or insect bites to the affected area.

A culture may be necessary to confirm the impetigo diagnosis or to rule out another cause. During this impetigo test, your doctor uses a sterile swab to gently remove a small bit of pus or drainage from one of the sores. The sample is then cultured in a laboratory for the presence of bacteria.

Differential Diagnosis of Nonbullous Impetigo:

Atopic dermatitis - Chronic or relapsing pruritic lesions and abnormally dry skin; flexural lichenification is common in adults; facial and extensor involvement is common in children

Candidiasis - Erythematous papules or red, moist plaques; usually confined to mucous membranes or intertriginous areas

Contact dermatitis - Pruritic areas with weeping on sensitized skin that comes in contact with haptens (e.g., poison ivy)

Dermatophytosis - Lesions may be scaly and red with slightly raised “active border” or classic ringworm; or may be vesicular, especially on feet

Discoid lupus erythematosus - Well-defined plaques with adherent scale that penetrates into hair follicles; peeled scales have “carpet tack” appearance

Ecthyma - Crusted lesions that cover an ulceration rather than an erosion; may persist for weeks and may heal with scarring as the infection extends to the dermis

Herpes simplex virus - Vesicles on an erythematous base that rupture to become erosions covered by crusts, usually on the lips and skin

Insect bites - Papules usually seen at site of bite, which may be painful; may have associated urticaria

Pemphigus foliaceus - Serum and crusts with occasional vesicles, usually starting on the face in a butterfly distribution or on the scalp, chest, and upper back as areas of erythema, scaling, crusting, or occasional bullae

Scabies - Lesions consist of burrows and small, discrete vesicles, often in finger webs; nocturnal pruritus is characteristic

Sweet's syndrome - Abrupt onset of tender or painful plaques or nodules with occasional vesicles or pustules

Varicella - Thin-walled vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop

Differential Diagnosis of Bullous Impetigo:

Bullous erythema multiforme - Vesicles or bullae arise from a portion of red plaques, 1 to 5 cm in diameter, on the extensor surfaces of extremities

Bullous lupus erythematosus - Widespread vesiculobullous eruption that may be pruritic; tends to favor the upper part of the trunk and proximal upper extremities

Bullous pemphigoid - Vesicles and bullae appear rapidly on widespread pruritic, urticarial plaques

Herpes simplex virus - Grouped vesicles on an erythematous base that rupture to become erosions covered by crusts, usually on the lips and skin; may have prodromal symptoms

Insect bites - Bullae seen with pruritic papules grouped in areas in which bites occur

Pemphigus vulgaris - Nonpruritic bullae, varying in size from 1 to several centimeters, appear gradually and become generalized; erosions last for weeks before healing with hyperpigmentation, but no scarring occurs

Stevens-Johnson syndrome - Vesiculobullous disease of the skin, mouth, eyes, and genitalia; ulcerative stomatitis with hemorrhagic crusting is most characteristic feature

Thermal burns - History of burn with blistering in second-degree burns

Toxic epidermal necrolysis - Stevens-Johnson–like mucous membrane disease followed by diffuse generalized detachment of the epidermis

Varicella - Thin-walled vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop