The only way to know for certain is to remove one item at a time. Stop eating the boiled eggs for several days but continue having the kefir. If nothing changes after about three days, stop the kefir and reintroduce the eggs the next day. If the problem continues after stopping each food, leave both foods out of your diet to see what happens. If the problem is corrected, then the cause could be the combination of the two. If the problem isn’t corrected after this, then it’s probably being caused by another source. This is using the elimination way of identifying a problematic food. If you have problems with adding foods after the cleanse, it may be wise to wait at least a few days between each item.