Diagnosis of Hot Tub Folliculitis

Clinical Diagnostic Criteria

Hot tub folliculitis is diagnosed clinically based on the characteristic presentation of pruritic papulopustular lesions on the trunk and extremities appearing 8-48 hours after hot tub exposure, with confirmation by bacterial culture of Pseudomonas aeruginosa from pustule specimens, as recommended by the American College of Physicians 1
The diagnosis requires recognition of the temporal relationship: Onset occurs 8-48 hours after hot tub, whirlpool, or spa pool exposure, according to the American Academy of Dermatology 1

It is essential to distinguish hot tub folliculitis from MAC hypersensitivity pneumonitis ("hot tub lung"), which presents with subacute dyspnea, cough, and fever from inhaled mycobacterial antigens rather than skin lesions, as stated by the American Thoracic Society 1
Hot tub lung requires compatible respiratory symptoms (dyspnea, cough) and characteristic radiographic findings (diffuse nodular infiltrates, ground glass opacities), with a strength of evidence rated as high by the American Journal of Respiratory and Critical Care Medicine 2
MAC isolates from respiratory specimens and hot tub water are necessary for the diagnosis of hot tub lung, with a moderate level of evidence supporting this requirement, as reported by the Centers for Disease Control and Prevention 2
Histopathology showing nonnecrotizing granulomas when biopsy is performed is also a key diagnostic feature of hot tub lung, with a high level of evidence supporting its use, according to the American College of Chest Physicians 2