Is it permissible to treat with pig fat as an ointment, and if permissible, does it affect ritual purity (tahara) and prayer (salat)?

It is not permissible to seek treatment with impure substances, such as pig fat, except in cases of extreme necessity, based on the Prophet's saying: "And do not seek healing with unlawful things." If one anoints his body with pig fat or other impure substances, his ablution is not invalidated, but his prayer is not valid until he washes the site of the impurity.