Tight Clothing = Itchy
These are my concerns with thrift stores:
1. Scabies
http://en.wikipedia.org/wiki/Scabies
2. Fleas of any kind
3.Head Lice
etc.
And the same fear goes to regular stores, but it occurs less because someone didn't wear it before.
All of these issues are easy to address, especially if you are buying washable cotton clothes; none of these things survive washing and drying machines, provided you use hot water and a heated drying cycle. I never try on thrift store clothes; I figure that we'll have a certain failure rate and that's part of why the clothes are cheap. I take them home, wash them, and THEN try them on, and just re-donate the ones that didn't work out.
Alternatively, none of these things survive without oxygen or contact with a host - if you buy something you think won't survive a hot water wash, seal it in a plastic garbage bag, squeeze out all the air and tie a knot in the top. Leave it for two or three days. (you should still was them or have them dry-cleaned.)
I've been shopping at thrift stores since I was in college, and never had trouble with any of the above.
the plastic bag is great for stuffed animals, and dress up clothing (off topic - I know).
As for plastics, you can wash them in the dishwasher, or if that is not possible make a 1:10 solution of bleach water in a spray bottle, spray them all over and let them sit for 24 hours.
I worked in a nursery (with kids who came from families w/those three problems) and we did all the above (some daily, some weekly, and some monthly): wash/dry, plastic bag rotation, dishwasher, and bleach spray.
I also shop from thrift stores, and do the wash/dry thing too. I have never had problems either. My children have caught lice several times from school though, so I worry more about that than thrift stores. I also got to visit the Goodwill central processing in Dallas once. They sorted everything, disinfectant sprayed everything that couldn't be washed, and had these huge industrial washer/dryers for all the clothes.
Anything you buy at a thrift store you can wash in hot water and dry in a dryer on the hot setting, it will kill scabies and head lice. All the things listed you can get....and my kids have had head lice many many times.....from going to school. Head lice is more common but you can get scabies. My daughter got it from a boyfriend who worked in landscaping and the doc says that is probably how he got it so you can get it from the dirt. Also people dont get fleas only animals and they can only live on animals and can not live without blood (same with head lice) for more than a day or so. Also they do wash the clothes at thrift stores but I wash them again when I bring them home.
They will put everything in a bag and you just toss it in the wash....I understand I have OCD issues like this too and I wont even wear new clothes before I wash them!
Also, never believe anything you read on wiki .
Also, never believe anything you read on wiki

Wiki doesn't say you can get them from thrift stories. I look things up for fact. Fact Head Lice exist, Fact head lice lays Nats, etc. All this fact is on Wiki, fact I know thus it is fine to read on Wiki. There is nothing wrong with wiki.
It's just my OCD of other people wearing the clothes before. Other people I don't know.
Also, never believe anything you read on wiki

Wiki doesn't say you can get them from thrift stories. I look things up for fact. Fact Head Lice exist, Fact head lice lays Nats, etc. All this fact is on Wiki, fact I know thus it is fine to read on Wiki. There is nothing wrong with wiki.
It's just my OCD of other people wearing the clothes before. Other people I don't know.
Actually there is tons of inaccurate facts on Wiki but there is also some good info. I have five kids, Im am a certified expert on head lice. I refuse to use chemicals on my kids heads over and over besides those little suckers are immune to that crap. It takes a lot of washing what you wear, sleep with or on in HOT water....you can also put stuffed animals in the freezer in a bag or in a bag outdoors if its cold for a day or two. Then wash your hair in real coconut shampoo with some tea tree oil mixed in and comb with a nit comb.....repeat this for three days. You can also use the mayo method where you cover you head with mayo or some other type of oil and a plastic bag (not your face of course) or one of those head coverings for a day or all night then wash your hair and again comb out nits and dead bugs. One time my daughters school could not get rid of them (hehe RID)...anyway, I had to braid my two daughters, who are now adults, head in tiny little braids and cover it and their scalp with baby oil. I would have to take out the braids at least twice a week, wash their hair and do it again. It was the only way to keep them out of their hair....one poor little girls Mother shaved her head because she had three boys maybe, I dont know....I felt sorry for her, she had to wear hats and my daughter said the other kids called her "cancer girl".....kids are so sweet!