Gut health eczema and food allergies

Me

My 20 month old son has had severe eczema and many fruits veggies trigger it off. He is constipated often. Was on formula and baby food. I had a second baby so I’m now pumping milk for my son. His poop has an apple vinegar smell. He’s always bloated and has bad gas. Been to many drs and specialists, none can help me. I want to detox him, any ideas how?