Is it possible that psoriasis can cause toe nail fungus i believe i have psoriasis on my foot according to research ?

Either one, or both.: When one has psoriasis on the skin, they can also have it in the nails. This is known as psoriatic nails. To complicate matters, one can also have a fungal infection involving the nail at the same time. This is called onycomycosis. So, as a result, you can have either condition, separately, or both, together. By nail appearance, both conditions can look very much alike, but treated differently.