My son is 7 months old now and still on number 1 milk. I’ve seen the follow on milk and wondered if I should put him on it? Is it a must? What are the advantages or disadvantages of it? My son had a reaction to aptamil when he was little and then suffered with reflux and regurgitation. His only been on normal milk for 3 1/2 months. Is it too soon to introduce another milk?