Why is there a discoloration on the armhole seams of my shirts?
Some manufacturers may use adhesives or other materials in the armhole seams on men's wrinkle-free shirts. This material is used to prevent puckering of the armhole seams if washed at home. When this material is commercially pressed , the heat softens the material, which results in local staining and stiffness in the seams. On white shirts, the staining will often have a yellow or grey cast, while colored shirts may appear darker or shaded in the area. This damage may occur after the first cleaning or may not show up until later cleaning and pressing.
Prevention of this damage is not possible since it cannot be identified prior to cleaning. The damage has usually been seen on wrinkle free shirts made with a cotton/polyester blend. Some of these shirts are labeled wrinkle-free, while many others are advertised wrinkle-free even though they don't have a permanent label identifying them as such.