What would cause a baby to have frequent bowel movements (diarrhea)?

She is 4 and a half months old and is perfectly healthy otherwise. She is having only formula, she has been having frequent diarrhea since last Sunday, her bowel movements are a yellowish color. So now she is getting diaper rash. I’ve been putting on Desitin and making sure to change her diaper extra frequently. Diaper brand isn’t an issue. She has no other symptoms. She just frequently has diarrhea and because she is having so many bowel moments she’s getting diaper rash. What could be causing her to have diarrhea?
Answers

Zzz

A 4 month old with diarrhea for 5 days and you haven't called the doc?? Seriously????

Tri-Harder

I assume that, like anyone else with a modicum of common sense, you would've called the doctor after a couple days of diarrhea, which would've been Tuesday, Wednesday at the absolute latest. So what did the doctor have to say?

BOO!Bwilder

Not worried about dehydration?

Slabberdasken

Anything could cause diarrhea in children. You have to be very careful with diarrhea in young children, especially if it is caused by the Rota Virus. It is DEADLY. If she gets worse, seek immediate medical help.

Jose

Probably a stomach bug. Do your best to keep her hydrated.

Jackie M

Probably teething or a stomach bug but when you wash her butt use Vaseline or petroleum jelly to prevent the diaper rash