This Halacha is an excerpt from our Sefer
General laws applicable on fast days:
Rinsing the mouth: On a public fast day, one is not to rinse his mouth in the morning. This applies even if one will be using less than a Revius of water. [If, however, this is causing one discomfort, he may be lenient to rinse his mouth.] On a private fast day, it is permitted to rinse the mouth with water, even if one uses more than a Revius. It is however forbidden to rinse the mouth on a private fast day with other liquids if they contain more than a Revius. If however the liquids are not drinkable, such as vinegar, then it is permitted to use even more than a Revius [on a private fast day].
Chewing tobacco/gum and other flavored items: Some Poskim rule it is permitted to chew and spit out all flavored inedible items, such as cinnamon, sweet wood, and spices of the like, on all fast days other than Yom Kippur. Other Poskim rule it is forbidden to chew any flavored item on any of the public fast days, and so is the final ruling. [Thus, one may not chew gum on a fast day unless it has no taste/flavor and does not contain moisture which gets swallowed upon the initial chewing.]
Bathing, anointing, wearing leather shoes, and marital relations: It is permitted to bathe, anoint, wear leather shoes, and have marital relations on a fast day other than Tisha B’av. [Nevertheless, a Baal Nefesh is to be stringent not to bathe [in hot water, if it does not involve a Mitzvah], anoint, or have marital relations on the fast day, just like on the ninth of Av. These stringencies begin from the night of the fast day, which is from the night of the 17th of Tammuz. Leather shoes however may be worn according to all. Likewise, on the night of Tevila one is not to abstain from marital relations with his wife. Some Poskim rule that in addition to the above stringencies, if possible, one is also to avoid doing any of the actions prohibited during the nine days, between Rosh Chodesh Av and Tisha B’av. Other Poskim negate this stringency, and say the stringency of a Baal Nefesh only applies to the five enumerated oppressions, and not to other matters.]
May one brush his teeth on a fast day?
If not doing so will cause one pain or discomfort it is allowed.
May one use mouthwash if not doing so will cause pain and discomfort?
Yes, it may be used in such a case.
May one eat meat and drink wine on the night of a fast?
Some are accustomed not to do so.
May one get a haircut on a fast day?
May one do laundry on a fast day?
Yes. However, there is room to learn that a Baal Nefesh should be stringent to avoid doing so.
May one listen to music and dance on a fast day?
Some Poskim rule it is forbidden to listen to music or dance from the night of the fast. Practically, in any event the custom is not to listen to music or dance throughout the three weeks, starting from the night of the 17th of Tammuz, as explained in chapter 2 Halacha 3.
May one get married on a fast day?
It is permitted to get married on a fast day. However, some Poskim disencourage one from getting married on a fast day, starting from the night of the fast. One may however according to all have the Chuppah take place during the day and arrange the music and dancing for the night. Practically, in any event the Ashkenazi custom is not to get married throughout the three weeks, starting from the night of the 17th of Tammuz, as explained in chapter 2 Halacha 1.
May one go swimming on a fast day?
Yes. However, some Poskim rule that a Baal Nefesh is to be stringent not to go swimming on a fast day, starting from the night of the fast.
May one recite Shehechiyanu on a fast day?
In general, it is permitted to recite the blessing of Shehechiyanu on a fast day. However, the custom is not to recite Shehechiyanu throughout the three weeks, starting from the night of the 17th of Tammuz, as explained in chapter 2 Halacha 4!
Giving charity on a fast day:
 Michaber 567:3 “One who is accustomed to rinse his mouth, it is improper-not Kosher- to do so on a public fast day” based on Terumos Hadeshen 158 regarding the prohibition to taste foods on a fast; Mamar Mordechai 567:2; Levush 567; Nehar Shalom 567:1; Bigdei Yesha 567:6; Kaf Hachaim 567:13; Chayeh Adam 132:20; Ketzos Hashulchan 2 footnote 25 in name of Ateres Zikeinim; Sefer Haminhagim p. 4 [English]
Other opinions: Some Poskim rule it is permitted to rinse one’s mouth in water even on a public fast day, with exception to Tisha B’av and Yom Kippur. [Drashos Maharil, brought in Darkei Moshe 567:1 and Elya Raba 567:5 and Kaf Hachaim 567:14] The Elya Raba ibid concludes one may be lenient if he is accustomed to do so daily.
Stringency or prohibition? It is implied from the Michaber ibid that there is no prohibition involved in rinsing the mouth even on Yom Kippur being one has no intent to swallow the liquid and it is merely water. [P”M 567 A”A 6]
 The reason: As one may come to swallow the water. [Mamar Mordechai 567:2; Levush 567, brought in P”M ibid]
 Machatzis Hashekel 567:6; Nehar Shalom 567:1; Bigdei Yesha 567:6; Kaf Hachaim 567:13
Other opinions: Some Poskim rule it is permitted to rinse one’s mouth with less than a Revius of water, as the entire prohibition against tasting foods only applies on Yom Kippur and Tisha B’av. [M”A 567:6; See P”M 567 A”A 6 who questions his ruling; See also Machatzis Hashekel ibid who learns in M”A that only on a Tannis Tzibur that is not one of the four fasts is this allowed, however on the four fasts even less than a Revius is forbidden.]
 Chayeh Adam 132:20; M”B 567:11; Kaf Hachaim 567:14
 Michaber ibid; Terumos Hadeshen ibid
 M”A 567:7 based on Terumos Hadeshen ibid
 M”A ibid; Elya Raba 567:4; M”B 567:12; It is unclear if the M”A is referring to only a private fast day or even a public fast day. However seemingly he is referring to a private fast day, which is the discussion of M”A ibid, and so is implied from M”B ibid and so writes M”E 602 Alef Lamateh 3; Piskeiy Teshuvos 567 footnote 2.
 Rama 567:3; Ateres Zekeinim 567
 M”A 567:8; M”B 567:13
 See Michaber and Rama 567:3 and M”A 567:8 that ideally one may chew cinnamon for the sake of flavor although practically one is to be stringent by all public fasts; If however there is no flavor or swallowed moisture, then seemingly it is permitted according to all. Thus, one may continue chewing an old piece of gum on a fast day.
 Admur 90:14; M”A 567:8 in name of Aguda; Aruch Hashulchan 90:17; M”B 567:13
The reason: As one has no intent of eating upon swallowing the saliva. [M”A ibid]
Other opinions: Some Poskim rule it is forbidden to swallow saliva on Tisha B’av and Yom Kippur. [Bach 612, see Aruch Hashulchan ibid]
 Implication of M”A ibid; Piskeiy Teshuvos 567:2
 Michaber 550:2; Tosafus end of 2nd chapter of Taanis
Other opinions: Some Poskim rule the custom today is to prohibit taking a bath on a fast day, with exception to Erev Shabbos. [Bach 550; Levushei Serud 550; Ateres Zekeinim 550, brought in Shaar Hatziyon 550:8] This stringency applies to only hot water. [P”M 550 M”Z 1; Shaar Hatziyon ibid]
 The reason: The Sages did not decree against these matters on a regular fast, as majority of the congregation cannot uphold to this. [M”A 550:3 in name of Ran] This means as follows: Originally, the Sages decreed by each of the four fasts that all the five oppressions apply. Thus, in times that fasting is obligatory, such as times of war, all five oppressions must be kept by all fasts. However, today, since it is a time of peace and we only fast due to our accepted custom, it is not necessary to guard the other oppressions, as we never accepted this upon ourselves, due the reason explained in the M”A ibid. [Beis Yosef 550 in name of Ramban; Taz 550:1; Machatzis Hashekel ibid in name of Ran; M”B 550:6]
 P”M 550 M”Z 1; Panim Meiros 2:49, brought in Shaareiy Teshuvah 550:2; Shaar Hatziyon ibid
 Such as Tevila. See Kesav Sofer 100; Piskeiy Teshuvos 550:6
 M”A 550:3; Shlah; Ateres Zekeinim 550; M”B 550:6
 Shaar Hatziyon 550:9 in name of Elya Raba in name of Shla; Poskim ibid-just like Tisha B’av; Thus, a Baal Nefesh should begin fasting from the night before, just as on the ninth of Av. However, see Piskeiy Teshuvos 550 footnote 18 that the custom is not to be stringent regarding fasting; See Shaar Hatziyon 565:8
 M”A ibid; Shlah ibid
The reason: As this appears like foolishness to the public. [ibid]
 M”A ibid; M”B 550:6
 P”M 551 A”A 10 based on Elya Raba “On the 10th of Teves and the 17th of Tammuz, if possible, one should be stringent like from Rosh Chodesh until the fast”; Biur Halacha 551:2 “Merosh Chodesh”; This positioned is also implied from the following Poskim who negate other actions on fast days: Peri Hasadeh 4:62 [weddings]; Ruach Chaim 564:4 [haircut]; Kitzur SHU”A 122:1 [music]; See Piskeiy Teshuvos 550:6-8
 Daas Torah 551:2 that the source of the P”M in the Elya Raba is based on a misprint
 Minchas Yitzchak 4:109; Piskeiy Teshuvos 567:1; based on Michaber 567:3 and M”B 11 who allows to rinse ones mouth in a case of pain
 See M”A 567:3 that one may rinse his mouth using vinegar, being it is not fit for drinking [accordingly, it is allowed even not in a time of need]; Kinyan Torah 2:49; See Mateh Efraim 602:3; Piskeiy Teshuvos 567 footnote 3
 Seder Hayom Inyanei Bein Hametzarim; See Piskeiy Teshuvos 550:8; 564:1
 Turei Even Rosh Hashanah 18b
 Ruach Chaim [Falagi] 566:4
 See Piskeiy Teshuvos 550:8 footnote 35
 Kitzur SHU”A 122:1; Even Yisrael [Fisher] 7:28; Piskeiy Teshuvos 550:7
 Rama 550:3; See also Igros Moshe
 Peri Hasadeh 4:62; Even Yisrael [Fisher] 7:28; Shraga Hameir 7:145; Even Yisrael 7:28 [permits on Taanis Esther]; See Mateh Efraim 602:5; Piskeiy Teshuvos 550:7
 See M”A 696; M”B 696:28; Yabia Omer E.H. 6:7; Igros Moshe 1:168; 4:112; Even Haezer 1:166; Piskeiy Teshuvos ibid
 Beir Moshe 3:77 rules it is forbidden to do so [however clearly this prohibition is only for a Baal Nefesh]; Piskeiy Teshuvos 550:6
 P”M 551 A”A 42
 See Tosafus Megillah chapter 3
 M”B 566:12