Intertrigo in the groin must be differentiated from psoriasis, candidiasis, and tinea cruris, though this may at times be challenging. Tinea cruris is a fungal infection characterized by red, scaly patches and plaques. The lesions form circinate plaques with scaly or papular borders and central clearing. After scales are scraped and 20% potassium hydroxide solution is added, the finding of hyphae in specimens under low microscopic power serves to differentiate tinea cruris from intertrigo. Candidiasis produces deep, beefy red lesions, often with characteristic satellite vesicopustules outside the border of the primary lesion. Involvement of the scrotum is common in candidiasis, whereas this area is often spared with tinea cruris. Psoriasis can affect all intertriginous areas. A clue to diagnosis on exam is involvement of the superior portion of the gluteal cleft (gluteal pinking).

Contact dermatitis may be caused by a variety of topical agents applied for the therapy of intertrigo or secondary to agents used for relief of pruritus or discomfort in the affected area. Often, the allergy is a secondary diagnosis in addition to the actual cause of the intertrigo. This diagnosis should be considered in patients with recalcitrant and itchy disease.

Other diagnoses that should be considered in the groin area are erythrasma, benign familial pemphigus, Fox-Fordyce disease, and hidradenitis suppurativa. Erythrasma, caused by Corynebacterium minutissimum, demonstrates coral red fluorescence under the Wood light. A condition known as benign familial pemphigus (Hailey-Hailey disease) should also be considered. In Hailey-Hailey disease, small blisters break down to produce the eruption. If an axillary lesion is nodular or raised, Fox-Fordyce disease and hidradenitis suppurativa enter the differential. Hidradenitis is suggested by chronic, painful, deepseated, inflamed lesions, nodules, sinus tracts, and abscesses often occurring in the groin and vulva premenstrually in women (see Chapter 114). The groin may also be affected by sexually transmitted diseases such as condyloma, herpes, scabies, and pediculosis. These produce an erythematous and pruritic eruption with characteristics that point to the underlying diagnosis (see Chapters 141, 192, 193, and 195). In severe cases of intertrigo, an underlying disease such as lichen sclerosus et atrophicus or lichen planus should be considered. Long-standing intertrigo with scratching often leads to the development of lichen simplex chronicus.