According to a professor of dermatology at Columbia University Medical Centre, new clothes can be contaminated with lice and fungus which is passes from human clothing from trying stuff on.
We don’t know who has tried clothing on before you have and how clean that person is. Infectious disease can be passed on through clothing. So even if you buy without the try- wash the clothes when you get home.
Another reason for washing them before you wear is that some chemicals used in clothes manufacturing process can irritate your skin.
Interestingly, 73% of those polled by the Today show already washed their new clothes before wearing, while 27% didn’t.