Service of a kohen who has something separating between his skin and his uniform, or his skin and the implement he is using - chatzitzah
Having a separation between one's hand and the utensils of the service during the service: Eruvin 103b-104a; Pesachim 57a; Zevachim 18a, 19a, 24a; Keritot 28b; Rashi Pesachim 57a "Karich"
Permitting a Kohen to replace a plaster on a wound after performing the service on Shabbat or Yom Tov (despite concern he might smear the ingredients), as otherwise he wouldn't remove the plaster for the service: Eruvin 102b; Beitzah 11b
Does air, from a gust of wind, constitute an interruption: Zevachim 19a
Are lice an interruption: Zevachim 19a
Do liquids, like blood, ink, honey and milk constitute an interruption: Shabbos 120b; Pesachim 65b; Zevachim 35a
Does dust constitute an interruption: Zevachim 19a
Does the air pocket in one's armpit constitute an interruption: Zevachim 19a
Does one's hand, thrust into one's garment, constitute an interruption: Zevachim 19a
Does a thread protruding from one's garment constitute an interruption: Zevachim 19a
Does a hair from one's head constitute an interruption: Zevachim 19a
Do one's tefillin constitute an interruption: Zevachim 19a