Clearly, the Ashkenazic custom to refrain from kitniyot cannot be stricter than the prohibition against ĥametz itself. Therefore, in extenuating circumstances like drought or famine, leading halakhic authorities permitted eating kitniyot. In actuality, rabbis have often disagreed whether the need was pressing enough to permit eating kitniyot. Some rabbis were inclined to be lenient, others to be stringent, and still others to permit kitniyot to the poor alone, requiring the wealthy to buy other types of foods. On such matters, one must follow the ruling of the accepted local rabbinic authorities.
Some Aĥaronim write that when applying these leniencies to kitniyot, it is better first to permit kitniyot that do not resemble cereal grain, and only permit rice, millet, and buckwheat when there is no choice (Nishmat Adam). Additionally, some Aĥaronim state that when applying these leniencies, one should first scald the kitniyot in boiling water, since scalding prevents even cereal grains from becoming ĥametz. Even though in practice we do not permit scalding cereal grains on Pesaĥ, when it is necessary to be lenient with kitniyot, it is best to take precautions as much as possible (Ĥatam Sofer OĤ §122; MB 453:7).
One who is ill and needs to eat kitniyot may do so, even if he is not dangerously ill. For example, one may swallow flaxseed with water as a laxative. One may likewise feed rice to children who need it (Ĥayei Adam 127:6), though special utensils should be set aside for this. Anytime one acts leniently, the kitniyot should be thoroughly inspected to ensure that they contain no cereal grains.
. Ĥayei Adam (127:1) permits eating kitniyot in truly extenuating circumstances, like if one has nothing else to eat. See also Nishmat Adam §20 and Mor U-ketzi’a (which assert that ideally the custom of kitniyot should be abolished altogether). Ha-mo’adim Be-halakha’s chapter on kitniyot states that Teshuva Me-ahava, Ma’amar Mordechai, and Mahariz Enzil maintain that one may not eat kitniyot even in an extreme situation. Conversely, Maharam Padua of Brisk (§48) permits kitniyot in extenuating circumstances. Divrei Malkiel 1:28 and Sho’el U-meishiv 2:4:158 rule leniently for poor people only. Ĥatam Sofer OĤ §122 does not oppose the lenient authorities but notes that they should require scalding the kitniyot before eating. Nishmat Adam §20 states that one should first permit kitniyot that do not resemble cereal grain, and only as a last option permit those that resemble grain. MB states that one may certainly be lenient in extenuating circumstances and cites Ĥatam Sofer and Ĥayei Adam that scalding is required before eating. AHS 453:5 states: “They explicitly accepted that if there would be famine and the poor would be starving for food, all of the local sages, led by the chief rabbi, would permit kitniyot on that Pesaĥ.”