This Halacha is an excerpt from our Sefer
One may not cut hair throughout the three weeks. [From the 17th of Tammuz until the week of Tisha B’av this matter is forbidden due to custom, while during the week of Tisha B’av it is forbidden from the letter of the law.]
Body hair: The prohibition against haircutting applies whether to the hair of the head, and whether to the hair of any other area of the body.
Mustache: One may trim any mustache hair that interferes with him eating. [This applies even during the week of Tisha B’av. However, some Poskim rule that during the week that Tisha B’av falls in, it is forbidden to trim any mustache hair, even if it interferes with food.]
Women: Some Poskim rule a woman may cut her hair throughout the period of the three weeks. However, other Poskim rule a woman may not cut or shave any hair of her body throughout the three weeks, just as is the law by a man. Practically, we are stringent. However, hair that is sticking out of a head covering of a married woman may be cut throughout the three weeks. Likewise, she may cut hair for the sake of immersion in a Mikveh throughout the three weeks. A wife may shave body hair for beauty purposes, to remain attractive to her husband, up until the week of Tisha B’av. Similarly, some Poskim rule that girls who are of shidduchim age may cut hair for beauty purposes, up until the week of Tisha B’av.]
Children: It is forbidden for an adult to cut a child’s hair. [This applies even if the child is below the age of Chinuch. Some Poskim rule this applies throughout the three weeks. Other Poskim rule it only applies the week of Tisha B’av. [Practically, in a case of need one may be lenient to do so.]
Avel/Mourner: If an Avel ended his Aveilus during the three weeks, he may cut his hair [even with scissors, up until to the week of Tisha B’av]. On the week of Tisha B’av, he may cut it with a razor, although not with a scissor.
It is forbidden for Ashkenazi men, women and children, to cut any hair of the body throughout the three weeks, with exception to mustache hair that interferes with eating, and hair that is cut for Tznius, or Mikveh purposes and the like, as explained above.
May a man trim his body hair?
No, as explained above.
May one brush his hair?
Some Poskim rule it is forbidden to brush the hair during the three weeks. Other Poskim rule it is permitted to do so. Practically, women may be lenient to do so, and the custom is to be lenient even for men.
May a woman pluck her eyebrows?
Sake of Mitzvah
When is an Upshernish to take place for a child that was born during the three weeks?
A child who was born during the three weeks is to delay the Upshernish until after the three weeks. It is to take place on the 10th of Menachem Av, after midday. However, all other customs relating to the Upshernish, such as wearing a Yarmulke and Tzitzis, saying morning blessings and the nighttime Shema, should already begin from when the child turns three years old.
May a Baal Bris get a haircut?
Some rule it is permitted for a Baal Bris to get a haircut even during the 9 days. Others rule it is permitted only until the week of Tisha B’av. Other Poskim rule it is permitted only until Rosh Chodesh Av. Other Poskim rule it is forbidden throughout the entire three weeks. Practically, the custom is to allow it until the week of Tisha B’av. The haircut may only be done on the day or night before the Bris. If Tisha B’av falls on Shabbos, one may be lenient up until Tisha B’av.
Pidyon Haben and other Simchos: The above leniency only applies to a Baal Bris, and not to any other Baal Simcha, even if one has a Pidyon Haben.
May a boy get a haircut during the three weeks for the sake of his Bar Mitzvah?
Time of need
May one fix a bad haircut?
If one began a haircut prior to the three weeks, then it is permitted to complete the haircut.
May one cut a child’s hair in order to remove gum that became stuck in it?
May one cut his hair as part of a medical treatment?
May one who is treating his hair for lice cut his hair?
May those permitted to take a haircut on Chol Hamoed also take a haircut during the three weeks?
If one is having a very important meeting, may he get a haircut beforehand?
Government officials: If one’s hair looks unpresentable and he is meeting with high government officials, then if his presence in this manner will be taken offence, he may be lenient to cut his hair. This however is to only be done with the official permission of a Beis Din, having them first annul his vow of his custom.
Business meeting: If one’s hair looks unpresentable and is meeting with other businessmen, then if attending in this manner may sabotage the business deal and cause him a financial loss, he may be lenient to cut his hair. This however is to only be done with the official permission of a Beis Din, having them first annul his vow of his custom.
 See Michaber 551:3
 Michaber ibid and Mishneh Taanis 26b regarding week of Tisha B’av; Rama 551:4 that we are accustomed to be stringent from the 17th of Tammuz; Beis Yosef 551 in name of Kol Bo that so is custom of Zekeinim
Ruling of Michaber: The Michaber ibid and Mishneh ibid rule it is only forbidden to cut hair beginning from the week that Tisha B’av fall in. However, prior to this week, it is permitted to cut hair. [Beis Yosef ibid; Kaf Hachaim 551:45] This is the ruling and practice of the Sefaradim.
For the sake of a Mitzvah: From the letter of the law, it is permitted to cut hair for the sake of a Mitzvah. [See Rama 551:2; Shivim Temarim 14]
 See Michaber and Rama ibid
 Michaber 552:12 regarding week of Tisha B’av and according to Rama ibid it applies throughout the three weeks; Michaber Yoreh Deah 390:1 and Moed Katan 18b regarding mourning; Tur in name of Ramban
 Michaber 551:13; Tur in name of Ramban
A Mohel: A Mohel may trim any hair that interferes with Metzitza. [Kaf Hachaim 551:172 in name of Ikarei Hadaat 27:11]
 Michaber ibid simply writes hair of the beard that interferes with eating. However we are accustomed to forbid cutting any hair of the beard other than the mustache.
 So is clearly understood from Michaber ibid who in the previous Halacha regarding haircuts only prohibits it on the week of Tisha B’av, and on this he states that trimming the mustache is permitted; Lechem Hapanim 122:3 in opinion of Michaber; Kneses Hagedola 551:13; Mateh Yehuda; Mamar Mordechai 551:12; Kaf Hachaim 551:170
The reason: As the week of Tisha B’av is similar to Shloshim, and not to Shiva. [Poskim ibid] And during Shloshim it is permitted to trim the mustache. [Michaber Y.D. 390:1; Maharitz Geios brought in Tur 390]
 Kitzur SHU”A 122:4; Ateres Zikeinim 551:13 that according to the Rambam and Raavad, brought in Shach 390:1 and Beir Hagoleh 390, and so rules Beis Yosef 390, that even within Shloshim it is forbidden to trim the mustache
 Panim Meiros 2:37; Ikarei Hadaat 27:19; Pischeiy Teshuvah
 The reason: As the Rif and Rambam rule a woman may cut her hair after Shiva by Aveilus, and thus here by Aveilus Yeshana, one may be lenient like their opinion. [ibid]
 P”M 551 M”Z 13; M”B 551:79; Kitzur SHU”A 122:3; Kaf Hachaim 551:47; Noda Beyehuda 14:99 regarding the week of Tisha B’av; See Lehoros Nasan 31; Igros Moshe 2:137
 Kaf Hachaim ibid
 Peri Megadim 551 A”A 13; M”B 551:79
 Shraga Hameir 7:36; Piskeiy Teshuvos 551:43 footnote 225
 Poskim ibid; Taharas Hamayim in Shiyurei Taharah 54; Mikveh Hamayim 7:12; Piskeiy Teshuvos 551:43
Shaving pubic area: This allowance includes shaving pubic hair for beauty purposes, so she does not become despised in the eyes of her husband. [Poskim ibid]
 Piskeiy Teshuvos 551:43; Halichos Beisa 25 footnote 70 in name of Rav SZ”A; Nitei Gavriel 21:3-4 in name of Poskim; See Lehoros Nasan 31; Igros Moshe 2:137
 So writes Piskeiy Teshuvos ibid “Only until the week of Tisha B’av”; however Nitei Gavriel ibid does not limit until when it may be cut.
 Michaber 551:14; Terumos Hadeshen 152
 The reason: As public mourning applies to children for Chinuch purposes. However private mourning does not. [M”A 551:38]
 Chayeh Adam 133:18; Ben Ish Chaiy Devarim 6; Shaar Hatziyon 551:91; Kaf Hachaim 551:173
 Elya Raba 551:31
 Chayeh Adam 133:18, brought in M”B 551:82 and Kaf Hachaim 551:175
 Piskeiy Teshuvos ibid and Nitei Gavriel 49:15 based on 531:6 and the commentaries there [M”B 531:6] regarding the allowance to cut a child’s hair during Chol Hamoed.
 Michaber 551:15; Moed Katan 17
 Implication of Michaber ibid; Taz 551:14; Bach 551
 Kaf Hachaim 551:46
 Mahariy Bruno 13; Kneses Hagedola 551:31; Mateh Yehuda 551 concludes to be stringent
 Elya Raba 551:7; Degul Merivava 551
 P”M 551 A”A 11; Ben Ish Chaiy Devarim 14
 P”M ibid permits in private; Shaareiy Teshuvah 551:12; M”B 551:20
 Piskeiy Teshuvos 551:43
 Shivim Temarim 14 [From letter of law is permitted, but nest is to differ until after]; Igros Kodesh 18:361; Igros Kodesh 24:355 [Do after Tisha B’av]; Shevach Habris 2:5 [Do on 10th after midday]; Mishnas Yaakov 551 in name of Satmar Rebbe; Chanoch Lanaar 21:22; Piskeiy Teshuvos 551:44 footnote 231that so is the custom
Other customs: Some Poskim rule one may even initially perform the Upsherinish if the child turn three years old up until; the week of Tisha B’av. [Nitei Gavriel 8:14 in name of Tzanzer Rebbe; Piskeiy Teshuvos 551:44]
 Shevach Habris ibid
 Igros Kodesh 24:355
 See Shaareiy Teshuvah 551:3; Kaf Hachaim 551:10; Piskeiy Teshuvos 551:6
 Panim Meiros 3:37; Chasam Sofer 158
 Elya Raba 551:28; Chida in Machazik Bracha 551:2; Zera Emes 76; P”M 551 M”Z 13; Or Nelam 10; Makor Chaim 551; Shaareiy Teshuvah 551:3 in name of Poskim; Binyan Tziyon 31; Kitzur SHU”A 122:15; Orchos Chaim Spinka 551 in name of Neziros Shimshon; Kaf Hachaim 551:10
 Beir Heiytiv 551:3; Beis Yehuda 2:85; Mateh Yehuda 551; Kitzur Shlah; Sheilas Yaavetz 2:63; Mur Uketzia 551; Noda Beyehuda Kama 28;
 Sdei Chemed Bein Hametzarim 1:7
 Kaf Hachaim 551:10; Piskeiy Teshuvos 551:6
 Sdei Chemed ibid; However, see 493:4 regarding Sefiras Haomer that it may be done the day before the Bris close to night.
 Elya Raba ibid; Binyan Tziyon ibid; Kaf Hachaim ibid; Piskeiy Teshuvos ibid
 Chasam Sofer ibid; Piskeiy Teshuvos ibid footnote 42
 See Piskeiy Teshuvos 551:6
 Mishneh Halachos 6:45
 Beis Avi 2:58; Shearim Hametzuyanim 120:8 Kuntrus Acharon
 See Piskeiy Teshuvos 493:11 footnote 82; P”M 493 M”Z 2 and Biur Halacha 493:2 that whatever haircutting is permitted on Chol Hamoed is permitted during Sefira; Regarding this allowance on Chol Hamoed see: Kapei Aaron 51; Chol Hamoed Kihilchaso 3:6 [p.122]; Piskeiy Teshuvos 531:2; See P”M 531 A”A 12
 This would seemingly follow the same leniencies as the previous case and following case.
 Aruch Hashulchan 493:3; Piskeiy Teshuvos 493:10; Nitei Gavriel Aveilus 3:13 regarding an Avel; See Chol Hamoed Kihilchaso 3:8 regarding Chol Hamoed, and the same applies during Sefira [P”M 493 M”Z 1; Biur Halacha 493:2]
 See Chol Hamoed Kihilchaso 3:8 regarding Chol Hamoed, and the same applies during Sefira [and the three weeks]. [P”M 493 M”Z 1; Biur Halacha 493:2]
 Aruch Hashulchan 551:34; So rule regarding Sefira: P”M 493 M”Z 1; Biur Halacha 493:2 “Nohagim”; See however Igros Moshe 2:96 who questions this ruling
 Nitei Gavriel 353 footnote 4
 Zera Emes 69; Machazik Bracha 493:4; Kaf Hachaim 493:19; See Chasam Sofer 158
 Igros Moshe 4:102