Hyperpigmantation under arm bit. it resolved completely after using dectarine solution for nail! now no dactarine sol in our market what to use pls?

Hyper pigmentation: Did you mean dactarin? I am not familiar with a "dectarine solution" for nails. Dactarin - or Miconazole - is an anti fungal agent and if that is what you have been using, if the etiology of your pigmentation is fungal, it might well have been effective. There are other causes of pigmentation, however, one being acanthosis nigricans - which would be unlikely at your age. Consult a dermatologist.

Miconazole: Dactarine is an anti fungal medicine. Fungal skin infections can cause hyperpigmentation. You can get it over the counter in the us under the name "miconazole.".