How-to whiten a dingy rayon blouse?

a kind of shirt made for women that is ususally button-down

Online it was described as a cheaper version of silk, so it probably has a silky feel.

Poor wording of the question. Cotton, silk, lycra? Check the tag.

a tube top is made of a 'tube' of cloth, that is usually a knit that is woven continuously without a seam. a strapless blouse is made of any material like cotton, linen, polyester, rayon , etc. that...

Yes. Very much so.Do not stand near hot surfaces such as an airtight stove or baseboard heaters. Rayon will heat up and can turn into flame very quickly.I learned that the hard way. =)