Can man made material shoes that look like real leather be used on yom kippur regading maris ayin? Are you also michsal others who might judge you wrongly thinking the shoes are real leather?
Today it is well known that there are many shoes that look like leather but are not in fact leather, and therefore there is no maris ayin in this matter.
This case is similar to questions of using parev creamer for coffee, or eating parev sausages with dairy products.
Chazal prohibited drinking fish blood, which is perfectly kosher, from a serving bowl, because it might be confused with animal blood.
Based on this Gemara, the Rashba (3:257) prohibited cooking meat in human milk, even though human milk is halachically parev. Similarly, the Rema prohibits cooking meat in “almond milk” – a white, milk-like liquid made from almonds which probably resembled our non-dairy creamer or soy milk – because of its similar appearance to cow’s milk. One may only cook meat in almond milk and serve it if one leaves pieces of almond in the “milk,” thereby calling attention to its non-dairy origin (Rema, Yoreh Deah 87:3).
The Pri Chadash (Yoreh Deah 87:6) disagrees with the Rema, contending that we should not create our own cases of maris ayin, and only prohibit those items that were prohibited by Chazal. The consensus of poskim is to prohibit these new maris ayin cases, following the position of Rashba and Rama.
Based on this ruling, it can be argued that one should not serve parev non-dairy creamer after a meaty meal, because someone might think that milk is being served after meal. Based on the analogy with the ruling of the Rema, it will only be permitted to serve the creamer if the original container, which clearly identifies it as a parev product, is kept close by.
However, Rav Ovadiah Yosef writes (Yabia Omer, Vol. 6, Yoreh De’ah 8) that a restaurant may serve non-dairy creamer with the coffee served at meat meals. The reason for this is because nowadays these creamers (and non-dairy milk) are common (and also because the person is not actually eating it with the meat), so that there is no concern for maris ayin.
The decision of Rav Ovadyah is based on a ruling of the Shulchan Aruch (Yoreh De’ah 298:1). Although it is forbidden, on account of maris ayin, to wear a combination of silk and wool – for the silk might be confused for linen – the Shulchan Aruch rules that “nowadays silk is common among us, and all know it, and therefore there is no problem of maris ayin, and it is permitted to wear it with wool or with linen.”
The same reason is employed by the Cheishev Ha-Efod (1:20) concerning spreading margarine and meat on one’s bread, and by the Shevet Ha-Levi (8:157) concerning eating parev schnitzel with cheese.
This will also be true of wearing “artificial leather” shoes on Yom Kippur.