Your toenails can thicken for many reasons. These include an injury; skin conditions, such as psoriasis; tight or poorly fitting shoes; and fungal infections — as shown in this picture.
Among these, a fungal nail infection — onychomycosis (on-i-ko-mi-KO-sis) — is the most common cause of thickened toenails.
Soften your toenails by soaking them for 10 minutes in warm water. Dry your feet and toenails with a towel. Now you're ready to trim them.
Nail nippers, work best. They're lightweight, easy to grip and control, and can be purchased at most drugstores. Nail nippers can be very sharp, however. Take extra caution when using them to trim your nails, especially if you have a disease that causes poor circulation or reduced sensation in your feet, such as diabetes or peripheral vascular disease; if you have any questions about trimming your own nails when you also have these conditions, talk to your doctor.
Starting at the corner of your toenail, take small cuts to prevent splintering. Don't round your toenail at the corner. Instead, cut straight across. This will reduce your chances of developing an ingrown toenail.
Take small, straight clips all the way across your toenail.
This thickened toenail has been trimmed correctly. The toes next to it need a similar straight cut. After the toenails have been trimmed, gently file the ends of the nails with an emery board to remove any sharp edges or corners that could catch on your socks. If you have a thickened toenail that's causing you embarrassment or worrisome pain, or if you believe that trying to trim your toenails on your own would be hazardous, see your doctor.