The newest USDA guidelines support early allergen introduction beginning at age 4 months, however, you can start RSF anywhere from 4-11 months of age. In doing my research into this brand, I discovered that many women who very reluctant to begin any kind of supplement before the age of 6 months, speaking particularly to exclusive breastfeeding moms. The most important thing to understand is that this is a personal choice that should be made in conjunction with your doctor’s consent and with your own personal thoughts, beliefs, and comfort levels.