Thick toenails come from a buildup of the cells that make up your toenails. Possible causes include increased age, nail fungus, peripheral vascular disease, and nail psoriasis (an autoimmune disease).

Common types of thick toenails include onychomycosis (a type of nail infection), onychauxis (a form of nail overgrowth), and onycholysis (when the nail separates from the nail bed). Onychomycosis ...