Couples showing affection in public:
Some Poskim rule it is forbidden even for a couple to affectionately touch each other in front of other people. [Thus, one may not hold hands, dance, hug, or kiss in public. Practically, so is the final ruling, and so is the custom amongst all G-d fearing Jews.]
It is forbidden for a couple to touch in public. This applies even towards non-affectionate touch, [if the touch extends for some period of time].
Walking together in public:
A couple must be careful to walk and talk in a modest fashion in public.
May one touch in public in an area without Jews?
May one clean something from his wife’s hair in public?
Seemingly, it is permitted to do so.
 Rama Even Haezer 21/5
 Nemukei Yosef Baba Basra 186b, based on story of Rav Benah and Eliezer, brought in Baba Basra 58a
 The reason: As it is not modest for a couple to be engaged in affection in public. In addition doing so will cause others to have erotic thoughts of them. [Taz 21/1]
 Kitzur SHU”A 152/11
 Beis Shmuel 21/12; Taz 21/1; Rashba 1188
Other opinions: Some Poskim rule it is permitted to check each other’s hair for lice in public so long as the head does not rest on ones body. [Derisha, brought in Taz ibid]
 The reason: As although it is not considered an act of affection which is immodest to do in public. Nevertheless, doing so will cause others to have erotic thoughts of them, as it reminds them of their intimacy. [ibid]
 See Brachos 43b that one is not to speak with his wife or daughter or sister in the marketplace; See Az Nidbaru 4/65 that the intent is that one must act in a modest manner; See Mishneh Halachos 10/217
 The reason: As doing so is immodest and may lead gentiles to have immoral thoughts also have a prohibition of Zera Levatala.
 As not all acts of touch are prohibited, as is seen from the fact one is not required to keep Harchakos in public, and we only find a prohibition mentioned regarding a touch of affection, or a touch of extended period of time, such as to check for lice.