No. If your baby had been allergic to anything in your system, he would have died before birth. Perhaps what your doctor meant is that your baby is allergic to a particular food in your diet. Your breast milk can contain protein fragments from foods, and if your baby is allergic to them, they can cause gas, rashes, reflux or other problems. To figure out if this is the case, eliminate from your diet the foods that are most likely to cause allergic reactions--dairy products, eggs, peanuts and soy--for two weeks. Then slowly add each one back in while monitoring your baby's reaction.