A 4 year old should bathe daily when they get dirty or sweaty.
However if the 4 year old is not getting dirty or sweaty then the 4 year old should only need to bathe every other day or 2 to 3 times a week.
Some 4 year olds and other kids are even fine bathing or showering once or twice a week if they don't get dirty or sweaty.
However if your 4 year old or kid is wetting the bed or having potty accidents then of course they should bathe daily to keep the urine from causing rashes and causing them to smell.
Even adults that don't get dirty or sweaty can go a few days between bathing or showering.
However in the summer when you're sweating or the kid is sweating or getting dirty or if you work job such as outdoors where you get dirty then of course you should shower to clean off.
Although once a kid is going through puberty such as over 11 it's recommended that the kid bathes or showers daily as they can produce more body odor during puberty.
After puberty hits, daily showering is essential due to new hormones flowing through the body bringing along unwanted body odor and acne.
Your child should also wash their face twice a day with a gentle noncomedogenic face wash.
By age 4 the child should be able to bathe themselves although you still want to be in the bathroom with them for safety and to ensure they are actually bathing and not just playing and or acting like they are bathing.
When your child can express their needs, understand instructions, and follow simple commands, it is a positive sign that they are ready to take on the responsibility of bathing independently.
By age 4 or 5, children often acquire the language skills necessary to comprehend and execute basic bathing routines.