Is a wet garment that has touched another dry, impure garment, or wet trousers that have touched impure underwear, judged to be impure if we doubt the appearance of traces of impurity, and is it obligatory to wash them in this case?

If the inner undergarment is wet with impurity, and you are certain that it has touched the dry or wet outer garment, then the impurity transfers, and it must be purified. However, if there is doubt about the contact, the ruling of impurity does not transfer, because the original state is purity. A person afflicted with obsessive whispering (waswasah) is advised to disregard it and not pay attention to it.