35a (Beraisa): The following are a Chatzizah (separation) if they are dry, but not if they are wet - blood, ink, honey, and milk.

98b (Rava): Blood on a garment is a Chatzizah (and disqualifies immersion), unless the owner is a butcher. Revav (a fat or wax stain) on a garment is a Chatzizah, unless the owner sells Revav;

Question (Rava): If blood and Revav are both on a garment, what is the law?

Question: Whether the owner is a butcher (and objects to Revav) or sells Revav (and objects to blood), one of these is a Chatzizah!

Answer: The question is when the owner is a butcher and sells Revav. He does not object to one stain, but he objects to two. Or, perhaps he does not object even to two stains!

This question is not resolved.

Chulin 106b (Beraisa): Any Chatzitzah that disqualifies Tevilah (immersion) also disqualifies Netilas Yadayim (washing the hands) for Chulin or washing the hands and feet in the Mikdash.

Eruvin 4b (R. Yitzchak): Mid'Oraisa, a Chatzitzah on the majority that he is Makpid (adamant) about is Chotzetz (invalidates the Tevilah);

Chachamim decreed to disqualify a (Chatzitzah on the) majority when he is not Makpid, due to when he is Makpid, and a minority he is Makpid about due to a majority he is Makpid about.

Question: Why didn't they decree about a minority when he is not Makpid, due to a minority when he is Makpid, or due to a majority when he is not Makpid?

Answer: Both of these are Chotzetz only mid'Rabanan. We do not decree due to a decree!

Yevamos 78a (Rava): If a (pregnant) Nochris converted, her child need not immerse.

Suggestion: Her Tevilah helps for the fetus due to R. Yitzchak's law. (Even though the mother covers most of the fetus, the fetus is not Makpid.)

Objection: Rav Kahana taught that if the entire body is covered, the Tevilah is invalid!

Answer: A fetus is different. Since he grows in his mother, she is not a Chatzitzah.

Rif (Berachos 41b): Any Chatzitzah that disqualifies Tevilah also disqualifies Netilas Yadayim for Chulin.

Rambam (Hilchos Berachos 6:4): Any Chatzitzah that disqualifies Tevilah also disqualifies Netilas Yadayim.

Rambam (Hilchos Mikva'os 1:12): There may not be a Chatzitzah between the person or Keli immersing and the water. If dough or mud was stuck to one's skin or a Keli, the Tevilah did not help. He or it is still Tamei. This is mid'Oraisa if the Chatzitzah covered most of the person or Keli and he is Makpid about it and wants to remove it. If he is not Makpid about it and does not care if it goes away or not, it is not a Chatzitzah, even if it covers the majority. Similarly, if it covers the minority it is not a Chatzitzah even if he is Makpid about it. Mid'Rabanan, if there was any Chatzitzah that he is Makpid about, even on the minority, the Tevilah was invalid. This is a decree lest there be a Chatzitzah on the majority that he is Makpid about. It turns out that if there was on his skin or the Keli a Chatzitzah such as dough, pitch or similar things, even a drop like a mustard seed, if he is Makpid about it, the Tevilah was invalid. If he is not Makpid about it, the Tevilah was valid, unless the Chatzitzah was on the majority.

Rosh (Chulin 8:15): Any Chatzitzah that disqualifies Tevilah also disqualifies Netilas Yadayim, e.g. a bandage on his skin, Greek mud and potters' mud. We are not concerned for a Chatzitzah on the minority (of the hand) that he is not Makpid about (Eruvin 4b): Even though Rashi says that this is only regarding hair, but not regarding skin, one cannot say so, like R. Tam proved from the case of a pregnant woman who converted (Yevamos 78a) and Zevachim 98b.

Hagahos Ashri (Berachos 2:11): Or Zaru'a says that one must be careful about scab in a wound or a boil that healed and there is a scab over it.

Shulchan Aruch (OC 161:1): Any Chatzitzah for Tevilah is a Chatzitzah for Netilas Yadayim, e.g. a bandage on the hand.

Beis Yosef (DH v'Chosav Od): Sefer ha'Terumah cites a Tosefta that whatever is a Chatzitzah for Kelim is a Chatzitzah for Nidah, but not for Chulin. That refers to Netilas Yadayim in order to touch Chulin Al Taharas Terumah or Kodshim. Chulin 106b says that it is a Chatzitzah for Netilas Yadayim for a meal. Some explain oppositely, so they are lenient nowadays about Netilas Yadayim. This is difficult, for the entire Sugya in Chulin discusses plain Chulin. Tosfos, the Rosh and Rambam say that whatever is a Chatzitzah for Tevilah is a Chatzitzah for Netilas Yadayim, and it seems that the Rif agrees.

Bach (3): In Siman 162, the Tur brings from the Rosh that it suffices to wash the rest of the hand. What is under the bandage is as if it were cut off. The bandage is not a Chatzitzah, for he need not wash there.

Taz (2): A bandage on his skin is a Chatzitzah if he has no wound, just it hurts, so he might take it off during the meal. If if he has a wound and he cannot take it off, he need not wash at all where the bandage is (162:10). Alternatively, also here we discuss when he has a wound, but he is not careful that the water on the bandage not return to the hand. Therefore, he wrote that if he is not Makpid, it is not a Chatzitzah.

Mishbetzos Zahav: If he is not Makpid about it, it is Batel to his hand, and it is like a normal Netilas Yadayim. If he is Makpid about it, it is not Batel, and the second pouring of water is not Metaher Tamei water on the bandage.

Kaf ha'Chayim (6): The Bach's opinion is primary.

Kaf ha'Chayim (7): Hilchos Ketanos says that if the bandage fell during the meal, he need not wash again, for it was not a Chatzitzah. It is as if he washed there (according to the Taz). The Birkei Yosef says (like the Bach) that it is not as if he washed there. Netilas Yadayim must be all at once, so he must wash the entire hand again.

Mishnah Berurah (4): The bandage has an ointment on it.

Shulchan Aruch (2): Anything that one is not Makpid about is not a Chatzitzah. If some are normally Makpid about something and others are not, it is a Chatzitzah only for those who are normally Makpid. If a dyer's hands were dyed, the dye is not a Chatzitzah, even if it has substance. If he is not a dyer, if his hands were dyed, and the dye has substance, dry dye is a Chatzitzah, but wet dye is not.

Beis Yosef (DH v'Chosav Od): The Rashba says that dry dye is a Chatzitzah for one who is Makpid about it, but not wet dye. If people like him are not Makpid, but he is, we follow his intent, and is a Chatzitzah. Anything that one is Makpid about is the ultimate Chatzitzah. However, perhaps we say that his opinion is Batel to that of normal people. This requires investigation.

Gra (4 DH Aval): The Mishnah (Mikva'os 9:3) distinguishes between men and women, and between married and single women. Zevachim 98b distinguishes based on professions. A Tosefta says that strings (that tie threads) on an Oni's garment are a Chatzitzah if he is Makpid, and those of a Ba'al ha'Bayis are not. R. Shimshon (Mikva'os 10:4) explains Stam, an Oni is not Makpid, and Stam, a Ba'al ha'Bayis is Makpid.

Kaf ha'Chayim (18): Pnei Yitzchak says that we follow the norm even to be lenient, but the Rema, Maharshal and Lechem Chamudos are stringent. One must be stringent.

Kaf ha'Chayim (19): If almost everyone is Makpid, but he is not, we follow the norm to be stringent (YD 198:1)

Kaf ha'Chayim (20): If in most places places are Makpid, we follow them even in places where people are not Makpid.

Kaf ha'Chayim (24): People of a profession are not Batel to the majority of others.

Magen Avraham (7): Regarding a Safek, we are stringent for Tevilas Nidah, and lenient about Netilas Yadayim.

Magen Avraham (8): Ink is not a Chatzitzah for one who writes constantly.

Gra: Just like ink is a Chatzitzah only if it has substance, the same applies to dye, which was taught with it.

Mishnah Berurah (14): Wet ink it is not a Chatzitzah because it dissolves in water and the water reaches his body. The same applies to dyes with substance. Chatzitzah does not apply to a mere discoloration, even if it is black.

Shulchan Aruch (ibid.): If a woman normally dyes her hands for beauty, the dye is not a Chatzitzah. A scab on his hands is not a Chatzitzah if he is not Makpid about it.

Source: Beis Yosef (DH v'Chosav Od, citing the Rashba.

Mishnah Berurah (12): Women who dye their hands for beauty want the dye, so it is like their body and it is not a Chatzitzah even if the entire hand is covered.

Beis Yosef (DH Semak): Semak says that a dry boil or scab that he is not pained if it is removed, whether it is on the hand or under the fingernail, is a Chatzitzah. Sefer ha'Terumah says that a dry scab that he is not Makpid about or a scab that is painful (to remove it) is not a Chatzitzah. Even though we normally remove them when immersing the entire body, that is a stringency.

Mishnah Berurah (16): This refers to a dry scab that he is not Makpid to remove, because it is painful to do so.