A sick Child[1]
With regard to a sick child, various leniencies apply in the mitzvah of parents educating their child that would not normally be extended to an adult. For example, it is permitted for a child who is ill to eat even foods that are biblically prohibited when necessary for his health, and the father is not obligated to protest his actions, although in certain cases he may not actually feed him the foods, as will be explained. [Based on this principle, the Poskim rule that a child who requires chametz-based foods on Pesach for his physical development and health is permitted to eat them. In such a case, the father may arrange for the child to be fed through a gentile.] This same rule applies for any prohibition which the child may need due to his illness.
How ill?[2] The above allowance applies even if the illness does not rise to the level of pikuach nefesh and even if he is only slightly ill to the point that he is not defined as even a Choleh Sheiyn Bo Sakana [i.e. not bedridden].[3]
Having a gentile feed the Issur food to the child: In the event of even slight illness, a father may instruct a gentile to feed the forbidden food to the child, as explained in Halacha 8f.
Directly feeding the child the forbidden food: All the above allowance is with respect to the adult or father making the non-Kosher food available for the ill child, instructing a gentile to feed it to him, or simply not protesting the ill child if he is seen eating it. However, unless the situation involves pikuach nefesh [or the matter is needed as part of the general development of the child as explained next], it is forbidden for any Jew to directly feed the child Biblically prohibited food, even if the child is sick as explained in halacha 8a.[4] This restriction however applies specifically when the prohibition is biblical. If, however, the food is forbidden only by rabbinic law, it is permitted for a Jew to hand‑feed the child when he needs it, in cases where a gentile is not available to do so, as explained in Halacha 8C.
Child needs the Issur food for general development: A child who requires certain foods or supplements for the sake of his physical development—such as young children who medically need specific nutrients or foods to support their growth and overall health—may be given those foods even if he is not presently classified as slightly ill. In such cases, it is permitted to even directly feed the child these foods, as they are necessary for his development and wellbeing. Thus, it is permitted to feed a child food on Yom Kippur.[5] [However, if the foods involved are prohibited by biblical law, then ideally a Jew may not feed the child directly, unless the food is not intrinsically forbidden and is merely forbidden at a specific time.[6] However, if the food is intrinsically forbidden then the food may only be made available to him indirectly, such as by instructing a gentile to feed him, or through similar means, and may not be directly fed. However, some Poskim[7] rule that all general necessities may be fed even directly to the child, even if they involve a Biblical prohibition, and so seems to be the plausible ruling. Accordingly, if a child is in need of a certain non-Kosher baby formula for his general health and development, from the letter of the law, it may be even directly fed to the child. However, see next regarding the custom.]
Important Note Regarding Non‑Kosher Foods:[8] All of the above leniencies of non-kosher foods apply only when there is no suitable alternative available and when the food in question is genuinely necessary for the child’s health. Otherwise, the accepted custom is to be extremely stringent with regard to feeding a child non‑kosher food, even in situations where it may be technically permitted for health reasons. This is because non‑kosher food is understood to cause a blockage in the child’s spiritual soul (timtum halev) and to negatively affect character development, as explained in Halacha 8C and Chapter 2 Halacha 3.
[1] See Admur 343:5 regarding asking a gentile to feed him an issur if he is in need of it; 343:5-6 and 8 regarding directly feeding him an Issur Derabanon for a need; Admur 450:24-26 regarding the allowance by Chametz; M”A 343:3; Tosefes Shabbos 343:3; Kaf Hachaim 343:16; M”B 343:5; See Piskeiy Teshuvos 343:12; 450:5
[2] Admur 343:5; M”A ibid; M”B ibid
[3] The reason we permit even if not bedridden: In cases where a child is classified as choleh sheiyn bo sakana—for example, if he is bedridden—significant leniencies apply, even with respect to an adult, and certainly with respect to a child. Accordingly, there is nothing novel in permitting such leniencies in that situation. The novelty here is that even when a child does not reach this level of illness, many of the leniencies normally afforded to one who is ill may nevertheless still apply to him.
The reason we only permit by slight illness: As for why the child must nonetheless be at least slightly ill, and why it does not suffice to rely on the established rule that a child is treated like one who is non-dangerously ill with respect to the laws of Shabbat: this is because, absent any actual need, there is no allowance to permit a child to be given even foods prohibited by rabbinic law as explained in Halacha 8c, and all the more so with regard to foods that are biblically prohibited. [Ketzos HaShulchan 147, footnote 5] Accordingly, the only circumstance in which it is permitted to allow a child to eat forbidden foods is when the child is at least slightly ill and the food is necessary for his health, or even if he is not currently ill, when the food is required for his physical development. Furthermore, the concept that a child is considered “like one who is ill” applies only until a certain age and does not extend all the way until bar mitzvah. By contrast, the leniency afforded to one who is slightly ill applies until adulthood. [See Piskeiy Teshuvos 343 footnote 141]
[4] Piskeiy Teshuvos ibid footnote 143
[5] M”B 343:3
[6] Admur 269:3 “It is permitted to feed a minor before Kiddush, whether at night or during the day. One may not cause affliction to a minor, for the prohibition against actively feeding a child applies only when the food itself is intrinsically forbidden, such as non‑kosher food and the like. However, when the food is intrinsically permitted but the time is one during which eating is prohibited, it is permitted to feed it to a minor. Thus, minors are fed on Yom Kippur, even one for whom there is no concern of danger were he to fast.”; 471:10; 616:1 “Accordingly, it is permitted for an adult to feed a minor, give him drink, apply ointment to him, and wash him with cold water.”; Rama 612:10; 616; Magen Avraham 269:1; Tur 616; Sefer Hayashar Rabbeinu Tam Chidushei Hateshuvos 52; Rashba and Meiri Eiruvin 40b and Yevamos 114a; Mishneh Berura 269:1; Encyclopedia Talmudit Vol. 16 p. 187; This ruling applies even according to the stringent opinion cited by the Alter Rebbe, which prohibits feeding a child even a rabbinic prohibition as that stringency is limited to foods that are intrinsically prohibited in and of themselves, such as a piece of neveilah.
[7] See Piskeiy Teshuvos ibid footnote 143 based on M”B 343:3 who permits feeding eating and bathing child on Yom Kippur
[8] Rama Yoreh Deah 81:7 regarding an infant eating milk from a gentile, as explained in Shach 81:26; M”A 343:2; Tosefes Shabbos 343:2; Kaf Hachaim 343:11; Ketzos Hashulchan 147 footnote 4; Piskeiy Teshvuos 343:12