If only nail-strengthening products really existed! What I wouldn’t give for that, and I’ve tried them all. As it turns out, many of the products that claim to strengthen nails contain extremely drying ingredients such as formaldehyde or toluene, which do toughen the nail temporarily, but also make it more brittle. Formaldehyde goes by other names on ingredient lists, so watch out for names like toluene, toluene sulfonamide, and toluene sulfonic acid. Toluene and toluene-like ingredients are illegal in the state of California because of the serious health risks they pose, including cancer and respiratory problems.
Some formaldehyde-free nail strengtheners just coat the nail, like the ridge-filling products. So-called strengthening creams contain thick, waxy ingredients, like lanolin, that smooth over the nail and are hard to wash off. If you are good about reapplying these several times a day (sans polish, of course, because they can’t penetrate polish), you might just see a change in your nails, because they help protect the cuticle and prevent the nail from drying out, but it takes discipline. Keep in mind that you can’t wear polish over any kind of moisturizing product because polish won’t adhere to a moist, lubricated surface. You can apply these products over polish; but then they won’t help the nail, although they can moisturize the cuticle.