After ko pung nanganak nagdark yung underarm KO....how can i get rid of this...... Almost 2 mos na kasi dark padin

I think it has to do with the hormones. 17 months na yung daughter ko and may part na slightly dark pa din sa underarm ko. Pero naglighten na sya compared nung buntis ako. Wala naman ako ginawa to lighten it. Kusa sya naglighten.