This Halacha is an excerpt from our Sefer
A. General Laws:
Some are accustomed not to bathe [or shower] starting from Rosh Chodesh Menachem Av [which is a period of nine days]. Others are accustomed to only avoid bathing during the week of Tisha B’av. Practically, the Ashkenazi custom is to avoid bathing for nine days beginning from Rosh Chodesh Menachem Av. [Due to this custom, it is forbidden for Ashkenazim to bathe during the nine days. The widespread Sephardic custom is to allow bathing even in hot water until the week of Tisha B’av.]
Cold water: The custom is not to bathe even in cold water.
Washing face, hands and legs: One may wash his hands, face, and feet with cold water during the nine days.
May one bathe children during the nine days?
A child who is dirty may be bathed in hot water. Some write one is to only use warm water to bathe the child unless the child will not shower in it.
B. Bathing for medical reasons:
It is permitted to bathe for medical purposes. Thus, if a doctor recommended one to bathe daily for medical reasons, it is permitted to do so.
A Yoledes: A Yoledes may bathe during the nine days, if necessary. [Practically, she may take a hot shower if she is within seven days after birth. Past this time, she may only do so if she received instructions from a doctor.]
Skin ailment: It is permitted for one to wash one’s head [in even hot water] for medical purposes, such as to heal scabs and the like.
During the nine days, it is forbidden to swim in a pool, ocean or lake, whether to cool off or for mere pleasure and relaxation. [It is however permitted to swim prior to the nine days, although one is to avoid swimming in dangerous areas from the 17th of Tammuz and onwards, due to it being a time of danger.]
Swimming for medical purposes: It is forbidden to swim for purposes of exercise during the nine days. Those who require the exercise for medical reasons, are to find an alternative exercise during the period of the nine days. In the event that other forms of exercise are not available, or are not as beneficial, one may swim for medical reasons, as recommended by a doctor. This would include swimming for therapeutic exercise after a surgery, or from one who suffers from joint pains, arthritis, fibromyalgia, back pain, or one who is in need of physical therapy.
May a woman who is in labor shower in hot water?
May a pregnant woman take a hot shower?
May one bathe in medical hot springs, such as the springs of Tiberius, during the nine days?
It is permitted to bathe in hot springs for medical purposes.
May one enter into a sauna or steam room during the nine days?
No. However, some Poskim are lenient in this matter if one will not enter the water afterwards. It is forbidden according to all to enter the sauna and then enter the water to cool oneself off.
C. Bathing for hygienic purposes-To remove dirt or sweat:
One who is dirty due to sweat or other substance, may bathe during the nine days in order to clean himself from that substance. [It is thus permitted for one to shower for reasons of cleanliness and hygiene. Nonetheless, it is forbidden for one to remain in the water, or in the shower, for longer than necessary to achieve the above cleanliness. It is permitted to bathe for cleanliness even in hot water. However, some limit this allowance to only cold water. According to all, one may shower in slightly warm water. It is permitted to use soap and shampoo in order to remove the sweat and dirt. Some say one is to only shower in private when done for the above purposes.]
D. Bathing for the sake of a Mitzvah-Mikveh:
It is permitted to bathe for the sake of a Mitzvah.
Nidda-Women’s Mikveh and Hefsek Taharah: Based on the above, it is permitted for a woman to bathe in preparation for a Hefsek Taharah and bathe [Chafifa] and go to Mikveh even if it falls during the nine days. [The above baths and immersions may be performed even in hot water.] Furthermore, if ones Mikveh night falls on Motzei Tisha B’av she may perform Chafifa on Erev Tisha B’av [in hot water] if she will not be able to do so on Motzei Tisha B’av. [Other Poskim however rule she is to perform Chafifa on Erev Tisha B’av even if she is able to do it on Motzei Tisha B’av, and on the night following Tisha B’av she should again bathe and clean herself, and then immerse. Practically, some write that the accepted ruling is to perform the Chafifa only on Motzei Tisha B’av. However, others conclude that she is to perform the Chafifa on both Erev Tisha B’av and Motzei Tisha B’av as rules the latter opinion.]
Men’s Mikveh: One who immerses in a Mikveh every Erev Shabbos, may likewise immerse on Erev Shabbos during the nine days. [The same applies for one who is accustomed to immerse every Shabbos morning.] If, however, one does not immerse every Erev Shabbos, such as when he has a cold, or when he is busy, then he may not immerse this Erev Shabbos of the nine days. [One who is particular to immerse in a Mikveh whenever he is a Baal Keri [or daily prior to Davening] may likewise do so during the nine days. It is likewise permitted for a Sandek to immerse in a Mikveh. When immersing in a Mikveh, one is to immerse in a cold or warm Mikveh, as opposed to hot. If, however, one is unable to immerse in a cold Mikveh, he may immerse in a hot one. It is however forbidden to remain within the hot water more than necessary.]
E. Bathing on Erev Shabbos during the nine days:
Erev Shabbos Chazon: On Erev Shabbos Chazon [Parshas Devarim] one may bathe his hands, feet and head in cold water. Some allow one who bathes himself every Erev Shabbos, to wash his head [hands and feet] even in hot water. It is forbidden to wash the remainder of one’s body even with cold water. [Likewise, one may not use soap or shampoo to wash his head, hands or face. The above however only applies when bathing for purposes of pleasure. It is however permitted to bathe the body for reasons of cleanliness, as stated above in C, and so is an old age Chassidic custom to allow bathing the body [for cleanliness purposes] on Erev Shabbos Chazon. Accordingly, if one feels sweaty or dirty, he may shower even with hot water, until his body is clean. It is however forbidden to remain in the water for more time than necessary.]
Rosh Chodesh Menachem Av falls on Erev Shabbos: When Rosh Chodesh Menachem Av falls out on Erev Shabbos then one who is careful to bathe every Erev Shabbos is permitted also on this Erev Shabbos to bathe his entire body in hot water as usual. Furthermore, it is forbidden to be stringent in this matter. [One may likewise immerse in a hot Mikveh this Erev Shabbos.]
It is forbidden to bathe [or shower] during the nine days, even with cold water, with exception to one who needs to shower for medical reasons or for reasons of cleanliness, or for the sake of a Mitzvah.
 Letter of the law, or custom: From the letter of the law of the Talmud and Poskim, it is permitted to bathe during the nine days with exception to Tisha B’av itself. [Ran; Gra; See Kaf Hachaim 551:186] However the custom became to avoid bathing some time prior to Tisha B’av as a sign of mourning just like a mourner avoids bathing during Shloshim.
 1st opinion in Michaber; Tur in name of Avi Ezri
 2nd opinion in Michaber; Mordechai; Tur in name of Ramban; Rambam Taanis 5:6; Ran that only the Tzenuin are accustomed to prohibit
 Rama ibid; Levush; Terumos Hadeshen 150; All Acharonim Rabbanei Ashkenaz, brought in Kaf Hachaim 551:186
 Rama ibid uses the wording of Issur regarding Erev Shabbos Chazon
 Yabia Omer 5:41; Yechaveh Daas 1:38; Yalkut Yosef
 Rama ibid; Terumos Hadeshen 150 “In my youth I saw people swimming during the nine days and no one protested them, nevertheless one who is stringent is blessed”; Maharil brought in Beis Yosef; Kaf Hachaim 551:186
Other opinions: Some Poskim rule it is permitted to bathe in cold water during the nine days. [Rambam ibid; Ramban; Ran; Shulchan Gavoa 551:13 and 48 that so is the custom in Salonika to go swimming even on Erev Tisha B’av; Yabia Omer 5:41; Yechaveh Daas 1:38; Yalkut Yosef] Practically, each community is to follow their custom. [Kaf Hachaim ibid]
 Rama ibid regarding Erev Shabbos and the Poskim rule that the same applies throughout the week; M”B 551:94; Derech Hachaim 7; Kaf Hachaim 551:199; Misgeres Hashulchan on Kitzur SHU”A 122:11; [It is a Mitzvah to wash ones face and feet every day out of respect for G-d, as the verse states “For in the image of G-d he created man”.. See Kama 4:1; “Awaking like a Jew” 4:10]
Other opinions: There is possible implication from the Rama 551:16 that even washing of the face hands and legs is only allowed on Erev Shabbos.
 See Admur 616:3-4 regarding Yom Kippur; Piskeiy Teshuvos 551:52
 Chanoch Lanaar 21:4
 Kaneh Bosem 1:32
 Admur 613:1 and 614:1 regarding Yom Kippur; See Rama 551:16 that only for pleasure is it forbidden; M”A 551:40 regarding Yoledes; Mahariy Bruno 12; Kneses Hagedola 551:23-24; Elya Raba 551:35; Chayeh Adam 133:19; Derech Hachaim 7; Shaareiy Teshuvah 551:37; Kitzur SHU”A 122:12; Ben Ish Chaiy Devarim 16; Kaf Hachaim 551:187
 The reason: As only bathing that is done for pleasure purposes is forbidden. [See Rama ibid; Admur 613:1 and 614:1 regarding Yom Kippur]
 See M”A 551:40; Elya Raba 551:35; Chayeh Adam 133:19; Derech Hachaim 7; Kitzur SHU”A 122:12; Kaf Hachaim 551:187; Shaar Hatziyon 551:94; Piskeiy Teshuvos 551:50
 The reason: The M”A ibid rules a Yoledes may bathe during the nine days and states that even on Tisha B’av it seems that this is allowed, and then concludes that one is not to be lenient in this being that we are no longer accustomed to bathe that often. It is unclear if the M”A ibid is saying one should never be lenient, or is not to be lenient on Tisha B’av. The Poskim ibid understand like the latter approach, and hence a Yoledes may bathe as normal, if necessary.
 Piskeiy Teshuvos ibid
 Levush 551; M”B 551:97; Kaf Hachaim 551:197
 See Chapter 2 Halacha 8; Piskeiy Teshuvos 551:46
 Shaar Hatziyon 551:94
 Shaareiy Teshuvah 551:17 in name of Elya Raba and Kneses Hagedola; Shaar Hatziyon 551:94;
 Piskeiy Teshuvos 551:50
 Darkei Chaim Veshalom 665; Kinyan Torah 2:100 that so he witnessed by the Brisker Rav; Piskeiy Teshuvos 551:50;
 Piskeiy Teshuvos 551:49
 Mishmeres Shalom Kudinov 40:1
 Beis Shlomo 101
 Sdei Chemed 1:9
 Admur 613:1 regarding dirt and 614:1 regarding sweat, that even on Yom Kippur one may bathe to remove sweat and hence certainly it is permitted during the three weeks; M”A 614:1; Elya Raba 614:1 in name of Shibulei Haleket; Mamar Mordechai 614:1 in name of Rabbeinu Manoach; M”B 613:2; Aruch Hashulchan 551:37; Igros Moshe Even Haezer 4:84-4; Sheivet Haleivi 7:77; Shearim Hametzuyanim 122:12 [Perhaps this is the Mahadurah Basra]; Piskeiy Teshuvos 551:48; Rav Eli Landa related to me that his father, Rav Yaakov Landa, was very lenient regarding showers in Eretz Yisrael and other hot climates, for purposes of cleanliness. However one should try to use only warm water; See however Orchos Rabbeinu 2:133 in name of Chazon Ish who forbade showering even due to sweat.
 See Tosefes Chaim on Chayeh Adam 133:37; Piskeiy Teshuvos 551:48; Rav Eli Landa
 Aruch Hashulchan ibid
 Sheivet Haleivi ibid rules one is to use only cold water, and is to wash one limb at a time. See Piskeiy Teshuvos 551:48
 Shearim Hametzuyanim ibid
 Shalmas Chaim 4:19; Vayivarech David 74; Piskeiy Teshuvos ibid
 Vayivarech David 74; Piskeiy Teshuvos ibid
 Rama 551:16
 The reason: As only bathing that is done for pleasure purposes is forbidden. [Rama ibid; Admur 613:1 and 614:1 regarding Yom Kippur]
 Rama ibid
 Rama states “to wash a little as she normally does during the year”. Today, the custom is wash the entire body in preparation for Hefsek Taharah. [See Rama Y.D. 196:3; Divrei Chamudos 10:27; Sidrei Taharah 196:13; Ben Ish Chaiy Tzav 2:10; Taharah Kehalacha 16:6] It is however unclear if the intent of the Rama is to permit slightly bathing the entire body, as is the custom, or to only bathing the private area, which is the ruling followed on Tisha B’av and Yom Kippur. [See Taharah Kehalacha ibid footnote 23]
 Drashos Maharil Tisha B’av; Derech Hachaim 7; Kaf Hachaim 551:193 that so is implied from Chayeh Adam 133:19 and Kitzur SHU”A 122:12
 Derech Hachaim ibid; M”B 551:92; Kaf Hachaim 551:194
 Rama ibid; Agudah; Beis Hillel Y.D. 199; Elya Raba 554:9; Chayeh Adam 133:19; Derech Hachaim 7; Kitzur SHU”A 122:12; See Yoreh Deah Rama 199:4 that the Chafifa of Erev Shabbos when immersing on Motzei Shabbos is only a custom. See Kaf Hachaim 551:195
 M”A 554:10; M”B 554:18; Degul Merivava 551:3; Biur Halacha 551:16 “Im” based on Shach 199:9 that from the letter of the law the Chafifa must be done on Erev Tisha B’av; Kaf Hachaim 551:198; Kitzur Dinei Taharah 5:14; Taharah Kehalacha 18:22
 Kitzur SHU”A 122:12; Shiurei Sheivet Haleivi 199:4; Piskeiy Teshuvos 551:47
 Kaf Hachaim ibid; Kitzur Dinei Taharah 5:14; Taharah Kehalacha 18:22; and so I received from Harav Asher Lemel Hakohen
 M”A 551:41; Shelah p. 200; Elya Raba 551:37; Chayeh Adam 133:19; Derech Hachaim 7; Kitzur SHU”A 122:13; M”B 551:95
 Kaf Hachaim 551:202
 Ashel Avraham Butchach 551; Mishpatecha Leyaakov 40; Shevet Halevi 7:77; Tzitz Eliezer 11:57; Piskeiy Teshuvos 551:48
 Ben Ish Chaiy Devarim 16; Aruch Hashulchan 551:35; Kaf Hachaim 551:190; Ashel Avraham Butchach; Sheivet Haleivi 7:77; Tzitz Eliezer 11:57; Orchois Rabbeinu p. 133 in name of Chazon Ish
 Ben Ish Chaiy Devarim 16; Kaf Hachaim 551:190
 Derech Hachaim ibid; Kitzur SHU”A ibid; Kaf Hachaim ibid and Poskim mentioned in previous footnote; Tosefes Chaim on Chayeh Adam 133:37
 Tosefes Chaim ibid; Kaf Hachaim ibid
 Tosefes Chaim ibid; Piskeiy Teshuvos 551:48
 Rama 551:16
 Rama ibid
Letter of law or custom: Ideally, it should be permitted to bathe on Erev Shabbos due to Kavod Shabbos, just as we permit laundering clothing in honor of Shabbos. However, it is accustomed to prohibit bathing even on Erev Shabbos. [Darkei Moshe 551; M”A 551:14]
 Rama ibid; Maharil 17
 Chayeh Adam 133:19; brought in M”B 551:97; Kitzur SHU”A 122:13; Kaf Hachaim 551:201
Other opinions: The Rama ibid rules one may wash these parts only with cold water.
 Rama ibid
 Rama ibid; Darkei Moshe 551:7; M”A 551:41; Elya Raba 551:37
 M”A 551:41; Chayeh Adam 133:19; M”B 551:97; Kitzur SHU”A 122:13; Kaf Hachaim 551:200
 Mishmeres Shalom Kudinov 40:1; Rav Henkin that so is custom and so was custom of Chassidei Reisin; See Nitei Gavriel 43:2
The reason: As it is permitted to bathe for the sake of a Mitzvah, as well, according to Kabala, one is not to do any change between this Shabbos and other Shabbosim. [Mishmeres Shalom ibid]
 See Tosefes Chaim ibid; Piskeiy Teshuvos 551:48; Rav Eli Landa
 M”A 551:40 in name of Bach; Taz 551:16; Elya Raba 551:36; Rashal 92; first custom in Levush, brought in M”A ibid; Bach 551, brought in M”A and Taz ibid “The custom is not to forbid it and one who avoids bathing this Erev Shabbos Lekavod Shabbos is doing a sin”; Ateres Zekeinim 551; Derech Hachaim 8; Kitzur SHU”A 122:13; M”B 551:89; Kaf Hachaim 551:189
Other customs: Some Poskim rule it is forbidden to bathe this Erev Shabbos just like on Erev Shabbos Chazon, being it is the first day of the nine days. [second custom in Levush ibid; Peri Megadim 551 M”Z 16 “I have not seen people be lenient in this”, brought in Shaareiy Teshuvah 551:17]
 One who is not careful to bathe every Erev Shabbos: The Taz ibid implies that if one is not particular to bathe every Erev Shabbos then he may not bathe this Erev Shabbos. [Taz ibid concludes that only one who is careful to bathe every Erev Shabbos may be lenient like the Bach] However the Bach implies it is permitted even for one who is not particular and if one is particular then it is even a sin.
 Bach ibid, brought in Taz and M”A ibid
 Piskeiy Teshuvos 551:51