Generic irritant diaper dermatitis is characterized by joined patches of erythema and scaling mainly seen on the convex surfaces, with the skin folds spared.

[6] This may be due to diarrhea, frequent stools, tight diapers, overexposure to ammonia, or allergic reactions.

[7] In adults, the stratum corneum is composed of 25 to 30 layers of flattened dead keratinocytes, which are continuously shed and replaced from below.

These dead cells are interlaid with lipids secreted by the stratum granulosum just underneath, which help to make this layer of the skin a waterproof barrier.

[10] Diaper rash is also most likely to be diagnosed in infants 8–12 months old, perhaps in response to an increase in eating solid foods and dietary changes around that age that affect fecal composition.

[11] The link between feces and IDD is also apparent in the observation that infants are more susceptible to developing diaper rash after treating with antibiotics, which affect the intestinal microflora.

[12][13] Also, there is an increased incidence of diaper rash in infants who have had diarrhea in the previous 48 hours, which may be because fecal enzymes such as lipase and protease are more active in feces which have passed rapidly through the gastrointestinal tract.

[15] A wide variety of infections has been reported, including Staphylococcus aureus, Streptococcus pyogenes, Proteus mirabilis, enterococci and Pseudomonas aeruginosa, but it appears that Candida is the most common opportunistic invader in diaper areas.

[15][16][17][18] The diagnosis of IDD is made clinically, by observing the limitation of an erythematous eruption to the convex surfaces of the genital area and buttocks.

Possible treatments include minimizing diaper use, and using barrier creams, mild topical cortisones, and antifungal agents.

[6] Others claim the material of the diaper is relevant insofar as it can wick and keep moisture away from the baby's skin, and preventing secondary Candida infection.

As it is often difficult to tell a fungal infection apart from a mere skin irritation, many physicians prefer a corticosteroid-and-antifungal combination cream such as hydrocortisone/miconazole.