The same change can be made to each word below to create a new one.

SIN
MILD
CASH

HINT:
The change involves the same two letters.

Answers:

The letters EW can be added to each word to form a new one:

SINEW
MILDEW
CASHEW

Credit: LA Times Crossword
March 29, 2015
Melanie Miller
THE "ICK" FACTOR

Note: See also THAT'S DISGUSTING
NY Times Crossword - Mar. 7, 2004
Tyler Hinman
Posted May 23, 2012 under Same Letters Same Order