Candidal diaper dermatitis develops when sufficient moisture in the diaper area allows Candida albicans, normal flora in the mouth and gastrointestinal tract, to proliferate and invade the stratum corneum. The dermatitis usually begins around 6 weeks of age and is often associated with recent antibiotic use or diarrhea, although it can be seen without any inciting factor. It can occur in conjunction with oral thrush. Candida may also secondarily infect and exacerbate irritant diaper dermatitis, seborrheic dermatitis, and flexural psoriasis.

An alkaline pH in the diaper area predisposes a patient to candidal diaper dermatitis. In both children and adults, fecal bacteria further alkalize urinary pH, which increases the risk of candidal infections. Breast-fed infants have a lower incidence of diaper dermatitis than formula-fed infants, which is theorized to be secondary to a lower stool pH in the breast-fed infants. Furthermore, patients with a defective Th17 response are predisposed to recurrent cutaneous candidal infections.