If you've been avoiding bananas for a long time, and you are indeed sensitive to this delicious fruit, you'll probably experience a reaction within 24 hours of your banana challenge. However, in rare cases, you might have to eat a banana every day for a week before your symptoms reappear. I've read about this "slow build-up" effect in books, but didn't really believe it until I saw it first hand in both my food sensitive children. Maybe it's not that rare after all.
My adopted son John has had allergies ever since he came into our home some two years ago. His nose ran constantly, accompanied by a barrage of sneezes. With so many other problems, he certainly didn't need this added into the mix. We started him on Claritin, and that helped a little. As we refined his diet his allergies abated, and we took him off the prescription antihistamine. However, his allergies certainly weren't gone. He might be symptom free for weeks at a time, but then his allergies returned, almost as severe as they were in the beginning. Unlike all his other symptoms, they didn't vary day to day, so I wasn't thinking about foods. Instead I concentrated on environmental factors - those we could control and those we could not. If he reacted to pollen, like so many other Americans, we could at least keep the house closed and the air filters clean, so he wouldn't be aggravated while indoors. We also removed the carpeting from his bedroom and laid down a hard-wood floor. This, combined with hypoallergenic bedding, guaranteed a safe sleeping environment.
During an unusually difficult spring we purchased an electronic air purifier, but it didn't seem to help. There was no improvement because he wasn't reacting to pollen at all. It was the food all the time, but it would take another year to figure it out.
I didn't get a handle on John's allergies until Mary (his sister) came down with the same symptoms. Now we had two kids blowing and sneezing all day long. For the fifth time in two years I wondered if wheat was a problem. I took wheat out of their diets (again) and her allergies disappeared in a couple days. His did not, but this time I had objective evidence that it might, if I just stayed the course. I had to wait another week before John's allergies began to subside. I don't know if I ever would have made the wheat/allergy connection if I hadn't seen it demonstrated in his sister. This is not the first time I have combined data from both kids, and it won't be the last. Deriving the dietary constraints of either child without the other would be much more difficult.
Most people will abandon a dietary regimen (especially a strict regimen) in a couple days if they don't see positive results, but sometimes patience is a virtue.
As described above, Mary reacts to wheat in a couple days, but other foods build up gradually in her system. In an earlier article I said her asthma was completely gone - well not quite. It came back recently, in a mild form. We were able to combat it with child's Benadryl, but it brought back terrible memories, and told us we were going down the wrong path. As it turns out, she was reacting to dairy, but the reaction took a long time to develop. I had given her Breyer's vanilla ice cream, the safest ice cream on the market, every other day for several weeks before her asthma developed, and once I suspended all dairy it took another week for her asthma to clear up. Can she have ice cream every third day, or every fourth? I'm sure she's anxious to find out. Like all kids, she loves ice cream. Since this is a slow build-up reaction, we won't have a definitive answer for a long time.
Some autistic children challenge wheat every day for two weeks, then throw a party, because everything looks good. Cakes, cookies and muffins are back!! But after a third week, or a fourth, the debilitating symptoms return. Then it takes a full month, gluten free, to return to good health. In rare cases an autistic child may have to be off wheat for three or four months to realize a significant improvement. That's what they tell me anyways - I can neither confirm nor deny.
"All this couldn't be caused by that little piece of bread I just ate - I use to eat wheat morning noon and night! It must be something else."
But you'd be wrong. I have seen this heightened sensitivity in my kids and my wife. When Wendy finally stopped drinking milk for several days, and then tried a small glass, she was sick in bed for 12 hours. She use to consume dairy in much larger quantities, every day, and she was never that sick, but now that she was off dairy she had become super-sensitive. This has since abated under a program of prolonged abstenance and gradual reintroduction, but it illustrates the concept of heightened sensitivity, which is certainly not something you would expect at the outset.
If you have a chronic condition, and you suspect a food or food chemical is involved, you should avoid that food for at least two weeks and then eat it in moderation for another week. You may see an improvement on your first day of abstenance, or you may have to wait several days, slogging through some withdrawal symptoms along the way. Similarly, your symptoms may return 15 minutes after you reintroduce that food, or you may have to eat it every day for a week before your symptoms reappear. And when your symptoms return, they may be worse than they've ever been. The response profile is determined by the individual and the food, and is largely unpredictable. Whatever you do, don't give up.