How can i tell if my 6 month old daughter's diaper rash is due to food allergy?

She gobbles up all the foods I have given her, which are not that many. however she has been having random painful poops and every day this diaper rash seems worse. She has had only one diaper rash prior to this one and it wasn't as bad and went away in a couple days no problem. This time it has been 4 or 5 days and each day it seems to get worse.

The difficulty is, simply bringing solid food into her digestive system is often, all by itself, a cause of diaper rash. With my first child, this was the first age she got diaper rash - when I first introduced meats in particular. She has no food allergies (she's now almost 5 years).

But I know something about babies and food allergies, as my son, on the other hand, is under the care of a pediatric allergist, and is verified (both skin and blood testing) allergic to milk, dairy, peanuts, tree nuts, eggs, shellfish, coconut. He never had diaper rash of any significance, to this day (22 months).

If your baby has hives, ruddy rashy cheeks and or patches of eczema, call your pediatrician tomorrow to start working through the possible allergy issue. If your baby is not having eczema or hives, but just diaper rash, the good news it likely isn't allergy. But you can't say for sure so you should continue carefully following all of the advice about how to introduce babies to foods.

So, to help you start sorting it out, I suggest after using wipes, wash her bottom off with plain water and gently pat dry. The detergents in wipes, plus the changes in her poop due to diet change, is often the source of diaper rash - or rather, aggrevates it once its started.

Also use the highest % zinc diaper cream and thickest formula after every change (e.g. Desitin ORIGINAL or Triple Paste), and if the weather is nice, let her get some sun and fresh air down there.

Also, under the assumption that it could be an allergy and you will need to work with a ped. allergist, start keeping a detailed food and observations diary.

It probably is food related, though it's more likely to be an intolerance than an allergy. Acidic foods (citrus fruit, tomato, baked beans) commonly cause nappy rash.
To be sure, stop all solids except rice cereal. Once the rash has cleared up, reintroduce foods one at a time, waiting at least 4 days before starting another. If the nappy rash appears, you have found the offending food!! Continue to introduce foods slowly, one at a time, as more than one food may cause a rash.
If you stop solid foods and the rash remains, look for another cause. My daughter developed a nappy rash from the brand of baby wipes I was using. Her skin also reacted to one brand of nappy.
It's time to be a detective!!

It may be due to the foods, or it could be that the weather is getting warmer causing her to get a slight heat rash in her diaper...which gets irritated when the diaper is soiled.

Eliminate foods one at a time from her diet, if her rash clears up after you eliminate one of them then don't give her that food for a while, and try it again later...if it gives her a rash again, she's allergic. If not, then the rash was just a coincidence.

Eliminate one food at a time for 4 or 5 days in a row. When the rash clears up you will know which food is the culprit. (For my son it's the acidic foods that cause the rash - pineapple, strawberry, orange juice.)

Try eliminating the food one at atime and see if it helps, also if you are givingher juice, it could be the juice, so do the same with that.

if it were an allergy (to food) she would have out breaks. try to evaluate the liquids she takes in and take her to the pediatrician.