Must one wash his hands prior to touching a Mezuzah?
Some Poskim rule that one may not touch the parchment of a Megillah or Mezuzah unless one washes his hands prior to doing so, or holds onto it using a cloth. Others however rule that there is no prohibition in touching the parchment. Practically the widespread custom is not to be stringent and people hence touch and hold the Megillah/Mezuzah directly without washing hands. Nevertheless it is proper for every person to be stringent upon himself and avoid touching the parchment of a Kosher Megillah/Mezuzah anytime, unless he washes his hands beforehand, or holds onto it using a cloth.
 For a general discussion: See Shaareiy Teshuvah 691/4; Kaf Hachaim 147/5; Piskeiy Teshuvos 691/7
 Regarding Mezuzah: Teshuvas R. Akivah Eigar 9; brought in Pischeiy Teshuvah 285/4; Regarding all Kisveiy Kodesh: Rama 147/1 [stringency]; M”A 147/1 [forbidden]; Haeshkol Hilchos Talmud Torah 12; Mor Uketzia 691; Sheilas Yavetz [forbidden, brought in Machazik Bracha 691/3]; Elya Raba 147/1 [stringency] brought in Shaareiy Teshuvah 691/4
The Michaber 147/1 rules that it is forbidden to directly touch a Sefer Torah without a cloth. The Rama brings an opinion [Aguda and Tosafos] that extends this prohibition to all Kisvei Kodesh. The Rama concludes that the custom is unlike this opinion, although it is proper to be stringent if one did not wash his hands. The M”A ibid explains that in truth the reason that we are not accustomed to be stringent is because this prohibition only applies to Kisvei Kodesh that is written with ink on parchment and since our books are not written in this method it is thus permitted to touch them directly. The conclusion of the Rama that it is proper to be stringent is thus superfluous. However a Kosher Megillah which is written with ink on parchment retains the above restriction from the letter of the law and not just as a stringency. [M”A ibid] The Elya Raba ibid however concludes that the ruling of the Rama “it is proper to be stringent” is actually referring to a Kosher Megillah, and it is hence not required to be stringent from the letter of the law as rules the M”A.
 To note that this allowance of washing the hands beforehand only applies to a Megillah and not to a Sefer Torah. [See Kaf Hachaim 147/2-3]
 Radbaz 2/771; Shvus Yaakov 11; Panim Meiros 1/76; Shaareiy Teshuvah 691/4; Shev Yeak 11;
 Radbaz 2/771 [“we have never seen anyone stringent in this”]; Panim Meiros 1/76; Shaareiy Teshuvah 691/4
 Rebbe Akiva Eiger ibid; Pischeiy Teshuvah ibid; Shaareiy Teshuvah ibid; Keses Hasofer 19; M”B 147/4; Kaf Hachaim 147/7; Hagahos Chasam Sofer that his teacher Reb Nassan Adler was careful not to touch it directly and so was the custom of the Chasam Sofer himself.