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http://www.huffingtonpost.com/2013/10/15/thong-health_n_4026307.html
According to an in depth investigation by the Huffington Post, wearing a thong isn't excellent for your vagina if you're the type of lady who is prone to hoo-ha brouhaha/vagina infection :)
The problem with thongs, in addition to being uncomfortable is that they simultaneously smother the vagina while leaving the labia unprotected. Smothering can cause women with sickly vaginas to have a tougher time shaking problems, and can contribute to recurrence of unpleasant afflictions like yeast infections.
Here's another gross thing that thongs can cause: skin tags on your vulva. Due to a lack of coverage. yikes.
Wouldn't you rather have a visible panty line than a crotch infection?