You see that phrase quite a bit if you've ever researched stocks or mutual funds. While past performance can be indicative of the future, contexts change, circumstances change, so the investor must be careful not to rely solely upon that one factor when judging an investment.
Unfortunately, the phrase is sadly applicable to those dealing with food allergies. If there is a lesson to be learned from this interview with Pamela, Andrew's mom, it's that a food-allergic individual must be prepared for the absolute worst at all times. A few hives here, a few hives there--that may be all there is and if so, then be glad for it. But you never know when (or why, sometimes) full-blown anaphylaxis will hit.
I am so, so sorry for their loss. It is every food allergy parent's worst nightmare. She is very courageous to share her story, to remind those of us in her position, or even those who want to believe we're all making a huge fuss over next-to-nothing, to be forewarned and forearmed. We've been lucky--all of Ryan's accidental exposures resulted in localized hives. I'm taking this opportunity to remind myself that that may not be the case in the future.