There is one allergen associated with an allergy to pork and that is Sus s 1, this is a serum albumin protein.
There is some evidence of cross reactivity between eating pork and allergic reaction to cat skin. This is known as Pork-Cat Syndrome.
A more recent and commonly known syndrome associated with pork allergy is Alpha-gal syndrome. This is when a person is bitten by a tick. The tick passes on a carbohydrate called galactose-alpha-1,3-galactose (also known as alpha-gal). This carbohydrate causes an immune reaction to make IgE antibodies. This is an unusual syndrome as it is caused by a carbohydrate and not a protein and because it often causes delayed IgE allergic reactions unlike classic IgE reactions which are very quick.
In extreme cases there may be some cross reactivity between other foods containing serum albumin proteins. These foods include other meats such as beef and chicken.
This is also the case for Alpha-gal Syndrome, other mammalian and bird meats containing serum albumin may cause delayed IgE reactions.