I have been going crazy about this for months, I have around 6-8 quite expensive new t-shirts/ jersey tops (all 100% cotton) and they have ALL got the tell-tale holes but none of the explanations offered on various forums seemed to fit; I mainly travel by train so seat belt seems unlikely, I started washing them alone on a delicate cycle with delicate detergent and in those net laundry bags, so catching on the machine or on zips seems wrong, I rarely clean with chemicals as I have a cleaner and I certainly haven't done so in all the tops, I have no signs of moths in the house, don't tug and pull the front and don't have any rough edges on my worktops etc etc. So what could it be?!?!?!?! I had reached the point where I was scared to buy tops because I knew this would ruin them!!!
Today I was puzzling over it once again and decided to look at a t-shirt I have worn and which doesn't YET have the holes, here's what I found. Small silvery residue on inside exactly around the culprit bottom front area (see picture 1), and though no visible holes, when held up to the light, small 'weak' looking spots around the same area as the residue (see 2nd picture, a little hard to see here and more noticeable in reality, but they are the small vertical lines around the centre and are not visible on the 'safe' areas to the edges where there are no silver marks). I thought - those weak spots are just waiting to become holes when I next wash this; and the silvery residue - I thought it could only be from the top button on my jeans, so I rubbed the button on the inside hem of the sleeve and hey presto - the same marks!! So looks like the jeans button bangs/ rubs on the top, leaves the residue and makes it weak, and then the washing machine opens up the hole!! I am assuming at this stage it is a physical rather than chemical reaction. I'm going to try handwashing it very gently in water only and see the results, then machine washing it on delicate on its own in a laundry bag without detergent, then with detergent! If and when the holes come, hopefully the mystery's finally solved!! Obviously when people say they occasionally get the same holes on other parts of clothes too, this weakening could be caused by any small trauma to the fabric, it's just that the jeans button is a very common one, hence why this area is always mentioned as the main problem on various threads/ forums etc.