Split nails are typically the result of dryness, which can be caused by heredity, exposure to abrasive chemicals or even prolonged exposure to water, such as when washing dishes. Nails also tend to become more brittle as you age, so it is important to moisturize the nail as well as the surrounding cuticle and skin area. Using nail oils can also help prevent the problem. Try massaging a drop of oil onto each nail a few times a week, and you'll notice the look improve significantly.
Once your nail is split, take immediate action so it doesn't worsen. A break in the nail is not only annoying, it can also cause serious damage to the nail and lead to infection. To repair the split, you will need acrylic powder and liquid along with a fine brush. These items can be found at beauty supply stores. You'll also need a buffer, file, colored nail polish of your choice and a clear top coat. If you are in a jam, superglue can be used on the break to seal it temporarily, but will not provide the best overall look.
What to Do
Begin by gently buffing the nail that has been split to even out the top layer slightly. Continue by buffing and filing your other nails to your desired shape. Once the nails have been prepped, get your acrylic powder along with the partnering acrylic liquid. Pour a small amount of the liquid into a small container and dip your brush into it, then immediately dip the brush into the acrylic power and spread over the damaged nail. Apply it first to the break itself and then paint over the entire nail to create a thin, natural-looking coat that mimics your own nail.
Allow the acrylic to dry completely and use your buffer to smooth out any unevenness that may be apparent. Paint the nails with a base coat of clear nail polish, followed by two coats of your colored polish to camouflage the acrylic nail you have created. Apply one final clear top coat to your nails and allow them to dry completely. Your nail will be bound by the acrylic and will grow naturally.
If you don't have the time or the materials for this technique, purchase a small tube of superglue. You'll only need a tiny drop. Use a toothpick to apply the glue directly onto the break itself. Use the nail buffer extremely gently to even out the rough edges of the glue. This method is not as permanent as the acrylic and will probably have to be repeated every few days, but it is a good way to save your nail in the meantime.