Predisposing factors of toenail fungus include fungal infection elsewhere on the body in particular, tinea pedis, a fungal skin infection that usually begins between the toes. Further predisposing factors are chronic paronychia, a skin infection around the toenails, previous onychomycosis, wearing of occlusive and tight shoes, hyperhidrosis, participation in sports or fitness activities, nail trauma, poor nail grooming, use of commercial swimming pools, communal bathing, living with family members with fungal infection, poor health, genetic factors, immunodeficiency (in particular, acquired immune deficiency syndrome and transplant patients), diabetes mellitus, obesity, Down syndrome, psoriasis, smoking, peripheral vascular disease, venous insufficiency, hallux valgus, and asymmetric gait nail unit syndrome, AGNUS, which is the result of asymmetric shoe pressure on the toes and foot caused by ubiquitous uneven flat feet that affect the gait.