The Prohibition to Eat and Benefit from Chametz on Pesach
Just as one may not eat Chametz on Pesach, Hashem has likewise commanded us not to retain any Chametz in our possession on Pesach. It is similarly forbidden to benefit from Chametz on Pesach, as we have already explained.
Actual Chametz Which Becomes Inedible before Pesach
Actual Chametz, such as bread, which became burnt to a crisp such that it resembles charcoal (see Responsa Yabia Omer, Volume 7, Yoreh De’ah, Chapter 10) before the time when it becomes prohibited, for instance, a day or two before Pesach, may be kept in one’s possession on Pesach as long as it becomes inedible even for a dog since at this point, it is no longer classified as “food” (meaning it is classified as dust and ash) and it is not prohibited as Chametz at all. However, if during Pesach the Chametz was edible and one burnt it to a crisp during the holiday, it will still be prohibited to benefit from it since the prohibition of Chametz has already applied to it while it was in its edible state.
Eating and Benefitting from Inedible Chametz
The Rishonim disagree whether it is even permissible to eat bread which was burnt to a crisp on Pesach or if our Sages only permitted one to retain it in one’s possession. According to the Ba’al Ha’Ma’or and Rabbeinu Nissim (beginning of the second chapter of Masechet Pesachim), one may even eat from this bread on Pesach. On the other hand, the Rosh and other Rishonim are of the opinion that our Sages only permitted one to retain it in one’s possession and benefit from it but it is forbidden to eat it. Maran Ha’Shulchan Aruch rules in accordance with the latter opinion that one may not eat scorched bread on Pesach, even if it is completely inedible. Nevertheless, it is permissible to benefit from it.
Ink, Cosmetics, Shoe Polish, and Cigarettes which Contain Chametz
Based on this, one may write on Chol Ha’Moed Pesach using ink made from beer (which is a Chametz derivative of barley). Similarly, a woman may use make-up and cosmetics even without a special Kashrut certification for Pesach (as long as it has no taste). It is likewise permissible to use shoe polish made with Chametz mixtures on Pesach since these items are considered completely putrid and are not even edible by a dog.
Nevertheless, one should make certain that the polish was manufactured before Pesach, for if the Chametz it contains was still edible by a dog on Pesach and only later on during Pesach it became completely inedible, it is forbidden to use it as it has already become forbidden to benefit from in any event.
Similarly, one may smoke cigarettes on Pesach which may be stuck together using Chametz mixtures because this sticking agent is completely inedible. Nevertheless, we must point out that this is all with regards to the prohibition of Chametz on Pesach; nevertheless, smoking is prohibited nowadays since all doctors agree that smoking causes clear and apparent danger to one’s health and a smoker also causes danger to those around him. Thus, one who cherishes his soul should abstain from smoking (See Halichot Olam Volume 1, Page 265).