Is nail hardener harmful for nails??

I don't know anything officially, but from my personal experience nail hardener makes my nails break even faster. I have tried several brands, and all have the same effect, a day or two after I put it on, my nails start breaking off for one reason or another. What I have noticed works is the nutra nail serum. That way you are making the nails strong themselves, instead of just lacquering them with a hardener. But this treatment does take a while to actually see some results, about two to three weeks. The serum doesn't cost much, you can find it in most stores.

Usually weak nails are caused by lack of vitamins. Try altering your diet and eating more protein, foods with Vitamin B12 in them as well as calcium, iron, zinc and Vitamin C. Don't take zinc or iron supplements, though, because too much can make you extremely ill.

I wouldn't imagine so. If it was, how could it be legal to sell?

actually nail hardener is good for the nails BUT too much of it is dangerous because it damages your nail.if you want to have harder nail without using nail hardener you better use garlic.rub the garlic on your nails everyday and it will keep your nails harder and healthy.. oxboo23xo