Zugos-Avoiding eating or drinking an even number of foods or beverages:
According to the Talmud, one is to avoid eating an even number of food or drink but is rather to only eat an odd number of foods. This is due to worry of demons and damaging spirits. Nonetheless, a negative affect can only occur to one who is particular in this matter as one who is not particular, they are not particular with him. Practically, however, we are no longer careful in this matter today, and there is no need to be stringent to do so. Nonetheless, there still remain meticulous individuals who are careful in this even today.
 See Kaf Hachaim 170:20; Sefer Shemiras Haguf Vihanefesh [Lerner] 28
 Pesachim 109b “A person should not eat two, or drink two”; Tur 170 “Due to danger” [See Bach and Perisha ibid]; Taz O.C. 170:5
 Rashbam Pesachim ibid; See Meiri Pesachim 109b and Sefer Shemiras Haguf Vihanefesh [Lerner] 28 footnote 1 in length
 Pesachim ibid
 Beis Yosef O.C. 170; Elya Raba 170:14; Tosafus Yuma 77b and Chulin 107b “Today we are no longer careful in this as there is no longer any danger in this”; Tashbeitz 550; Maharikash 170; Machazik Bracha 170:2; Bris Olam 477; Aruch Hashulchan Y.D. 116:16; Kaf Hachaim ibid; See also Michaber 170:11; Sefer Shemiras Haguf Vihanefesh [Lerner] 28 footnote 1 in length
 Otzer Hachaim 112; Darkei Chaim Veshalom 287; Minchas Elazar 3:66-2
Custom of Chazon Ish: The Chazon Ish was accustomed not to eat an even number of eggs.