The significance of secondary infection in IDD remains controversial. There seems to be no link between presence or absence of IDD and microbial counts.  Although apparently healthy infants sometimes culture positive for Candida and other organisms without exhibiting any symptoms, there does seem to be a positive correlation between the severity of the diaper rash noted and the likelihood of secondary involvement.  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.    
Allergic sensitivity to a topical corticosteroid is usually only picked up when an eczematous dermatitis being treated by a topical corticosteroid fails to respond to treatment or worsens. In cases of persistent or exacerbating dermatitis treated with corticosteroid preparations, corticosteroid sensitivity should be considered. However, it may also be due to irritation from or allergy to other components of the preparation such as preservatives . Lanolin , ethylenediamine , quaternium-15 and the antibacterial agent neomycin , are all known to be potent sensitisers.