There are different levels of diaper rash and also other types of (baby) rashes:
Diaper rash can be ‘marked’ in different levels; light, mild, mild to moderate, moderate and severe. Each level has its own characteristics and visual appearance. Each diaper rash level comes also with its own (pain) related problems. Every baby creates it own specific rash also. Keep in mind that in a “light” situation, when the skin appears to be intact, the skin may be slightly damaged. The use of a product may give a (skin) reaction.
A baby’s rash may be something other than diaper rash, such as a yeast infection, psoriasis or impetigo. These rashes are more worse then diaper rash, definitely when they are present same time as diaper rash.
It is advised to call a pediatrician if a baby shows heavy symptoms without knowing what kind rash it is.