“Question: Is there any problem in using ThermaCare® heat wraps on Shabbos?
Background: ThermaCare® heat wraps consists of heat cells that contain a mixture of ingredients (iron, water, and salt) that react with air to provide low-level heat. The chemical reaction that occurs within is iron oxidation. Each heat disc is designed to heat to about 40°C (104°F) for 8 hours. ThermaCare® heat wraps work by allowing real heat (from the heat cell) to penetrate damaged tissue, which increases blood flow and accelerates the body’s natural healing process by relaxing the muscle and increasing blood flow in the area.
Discussion: Regarding using ThermaCare® heat wraps on Shabbos we need to analyse these products from a few different Halachic angles; bishul, makeh b’patish, molid and refu’oh:
Bishul – since the resulting temperature of the heat cells is only 40°C (104°F) this does not pose an issue of bishul, because this resulting temperature is under yad soledes bo (see sefer Shmiras Shabbos Kehilchoso perek 1 se’if 1 and footnote 3).
Makeh b’Patish/Molid – the heat cells work by utilising the reaction of iron oxidation, which occurs passively once the product is opened and exposed to air. Opening the packet merely allows iron oxidation to occur by itself and thus poses no problem of makeh b’patish or molid.
Refu’oh – The issur of refuoh includes taking medication to heal, relieve pain or to generally strengthen the constitution (see Shulchan Aruch Siman 328 se’if 1; Magen Avraham ibid s.k. 43; Mishna Berura ibid s.k. 120). Not only is standard medication forbidden; even physical activities that have a healing effect (e.g. exercise or physiotherapy) are prohibited – on condition that the same effect can be achieved through medication (see Shulchan Aruch Siman 328 se’if 42; Mishna Berura ibid s.k. 130; Shmiras Shabbos Kehilchoso perek 34 se’if 22; Orchos Shabbos volume 2 perek 20 se’if 159 and footnote 221).
Since the intention of heat cells is ultimately to heal and relieve pain, it is consequently included in the prohibition of refu’oh. Therefore, it may only be applied in a situation of choli (illness). The definition of a choleh is one who is ill to the extent that he is bedridden, or incapacitated (i.e. cannot function as normal), or experiencing severe (even localised) pain (Shulchan Aruch Siman 328 se’if 17; Mishna Berura ibid s.k. 1; Shmiras Shabbos Kehilchoso perek 33 se’if 1; Chut Hashoni perek 89 se’if 26).
However, if a person is feeling generally well, and is only experiencing moderate pain or an ailment, the prohibition of refu’oh applies and the heat wraps cannot be applied. It should be mentioned that there is no prohibition for anyone to apply the heat cell before Shabbos and the heat cell can remain in place and continue to provide pain relief on Shabbos (c.f. Mishna Berura ibid s.k. 81).
There is another significant leniency that should be noted: The Shulchan Aruch (Siman 307 se’if 5) rules that in a situation of a minor ailment (miktzas choli) it is permitted to ask a non-Jew to perform an issur d’rabonon. This leniency is called “shvus dishvus”. Since the prohibition of refu’oh is midrabonon, it is therefore permitted to ask a non-Jew to apply the heat cell, in a situation of moderate pain.
To summarise: ThermaCare® heat wraps pose no problem of bishul, molid or makeh b’patish and the only Shabbos issue is refu’oh. Therefore, they may not be applied by somebody who only has a minor ailment or slight pain (classified meichush and mitzta’er), and are only permitted in a situation of choli (illness) similar to regular medication.
As mentioned, a heat cell can always be applied before Shabbos so that it continues to function on Shabbos. Also, in a situation of moderate pain one can ask a non-Jew to apply the heat cell.
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