Case Presentation:

A 42–year–old female presented to the emergency department complaining of a six day history of left hand swelling, blisters, and itching. Physical exam showed extensive edema and erythema involving the left dorsal hand with scattered tense bulla measuring 1–3 cm involving the first through third digits. There was a loss of sensation to light tough over the thumb and index finger. She was afebrile, with a white blood cell count of 10, 000/ul with normal differential. Plain x–ray of the left hand showed extensive soft tissue swelling without subcutaneous emphysema. She was diagnosed with cellulitis and admitted for intravenous antibiotics and observation. Overnight, because of markedly worsening edema of the left hand, a presumptive diagnosis of necrotizing fasciitis was made and she was taken for emergent fasciotomy. Intraoperatively, there was no evidence of sot tissue infection or necrosis; tissue cultures grew non–hemolytic Streptococcus and coagulase–negative Staphlococcus which were considered contaminants. She was hospitalized for one week, during which time she continued receiving antibiotics. She was discharged on course of oral antibiotics with a presumed diagnosis of superinfected dermatitis. Two months later, the patient was re–admitted with a similar eruption involving the bilateral lower extremities. A more thorough history revealed the patient had been using Lanacane, an over–the–counter topical anesthetic for mild itch. A skin biopsy revealed spongiotic dermatitis, tissue immunofluorescent studies were negative. Patch testing confirmed allergic hypersensitivity to benzocaine, the active ingredient in Lanacane, and avoidance of topical benzocaine lead to resolution of the patient’s dermatitis.

Discussion:

Acute bullous contact dermatitis is not an uncommon presentation of allergic contact dermatitis and a thorough history must be elicited in order to clinch the diagnosis. Clues favoring a diagnosis of ACD are the presence of pruritus and bullae developing on a background of edema. Skin biopsies are helpful in ruling out other diagnoses, however, patch testing remains the gold standard in diagnosing ACD. Patch testing confirmed that our patient had allergic hypersensitivity to benzocaine, a topical ester anesthetic that is found in medicinal products including hemorrhoid cream, teething gels, and anti–itch products. Physicians should recognize the possibility of contact sensitivity to over–the–counter medicinal preparations; encouraging avoidance of these agents will lead to resolution of the dermatitis.

Conclusions:

Allergic Contact Dermatitis (ACD) is a form of delayed, type 4 hypersensitivity reaction. This is usually considered in patients presenting with well demarcated erythematous, scaly patches. However, tense bullae are not an uncommon presentation and unless this morphological subtype is recognized by the physician, the diagnosis may be missed.