I don't know why my bay is getting red rashes in arms,for last one month we revised infant formula and also start giving porage like cerala wheat.may be becoz of that... please answer

It may be due to the wheat. When do you notice the rash appear? Is it after a meal? Has it only happened since the change in formula and introduction of the wheat? Try stopping the wheat and see what happens. If it is due to the wheat you should notice a change quickly.

Did you change formulas for a particular reason? Did her doctor suggest the change?

If you find that stopping the wheat makes a difference, you should let her doctor know about your concerns. If there is no change, and since there can be a number of possible reasons for a rash, let her doctor know that as well so that they can try and determine what the cause may be.