I suspect it's sweet potato that cause sudden outbreak of eczema in my 7mo. I have removed it from his diet for a few days and he improved...how shld I confirm it? When can I try to introduce the suspect food again or he can't have it for life?

Once the outbreak clears, give it another 2 weeks before you reintroduce sweet potato again. Don't give me anything new except sweet potato. My lo was previously allergic to berries and tomatoes. I will feed it every 1.5months to see if he is still allergic to it (he gets itchy behind his knees and at his elbow). Eventually he stop itching at around 2 yrs old and he is eating lots of them now at 6 yrs old :)