Matthew Wagner writes in the Jerusalem Post:
Orthodox Jewish dietary stringencies on Pessah are considered obsessive-compulsive by some, but a way of cleaving to God's will by others.
Some stringencies even exceed the edible. There is aluminum foil that is kosher for Pessah, soap that is kosher for Pessah, even bleach that is kosher for Pessah - not to mention lipstick.
Hassidic sects, however, are the hands-down champions of Pessah strictures. The faithful say of Rabbi Mordechai Hager, the octogenarian Viznitz rebbe of Monsey, New York, that by the end of Pessah, the poor man can hardly stand on his own two feet. Hager does not trust the kosher supervision in the slaughterhouses of America so he does not eat red meat. He has abstained from chicken since the recent Monsey kosher poultry scandal. On Pessah, he eats matza only on the fist night of the holiday to fulfill the mitzvah. But for the remainder of the holiday, he refuses to touch the unleavened bread, fearing that there are pockets that did not bake properly and could, therefore, be hametz.
Like all Viznitz Hassidim, Hagar also refrains from eating fish. According to legend, the custom was born in Romania, the center of Viznitz Hassidism, before the Holocaust. Due to the harsh winters, Romania's rivers were usually still frozen during Pessah. Therefore, it was necessary to import fish from a great distance. One year, the Viznitz rebbe, for no apparent reason, refused to eat the fish that was brought. It was later discovered that the fish had been marinated in a grain alcohol that was not kosher for Pessah. Ever since, the hassidim have refused to eat fish.
Hager and other hassidim, especially Belz, do not eat carrots. According to legend, in Galicia it was nearly impossible to obtain vegetables for the Pessah seder. One year, the Belz rebbe managed to get a carrot. It later turned out that the carrot, like the fish, had been dipped in non-kosher-for-Pessah alcohol to be preserved.
Many hassidim also avoid garlic for fear it was cut with a non-kosher knife.
In addition, hassidim abstain from any vegetable that is not peeled, such as tomatoes and peppers, for fear that something non-kosher has stuck to it.
Shmuel Poppenheim, a spokesman for the Edah Haredit, an ultra-Orthodox umbrella group of hassidic sects and haredi communities, says that he and many other ultra-Orthodox Jews do not eat anything produced in a factory except for oil. That means no soft drinks, no ready-made baked goods and no canned foods.
Sugar is another problematic product because it may contain wheat flour.
Poppenheim, commenting on Rabbi David Bar-Hayim's recommendation to permit Ashkenazi Jews to eat kitniyot (legumes,) said that "Every Jews carries with him the customs he received from his father and his father's father. Smart alecks like [Bar-Hayim] think they can come along and change everything. We have to wait until [the Messianic era] when Elijah the prophet reveals himself and clarifies all the doubt and answers all the questions."
Elijah's gonna come and he's going to put these 'holy men' and their followers on a good course of Zoloft (no matter what binder is used in the pill-making process).