On one of my fall trips to GIG (before AA changed its policy on Q fares and therefore I was in Y) there was a young couple on the return (husband was a PLT) that sat in front of me. On their way down to GIG the young lady had wrapped the red blanket around her to stay warm. She ended up getting a rash that was so bad she needed to go to the emergency room in Rio (IIRC the two were on their honeymoon). I try to avoid those blankets unless that are wrapped in plastic and use my coat instead to stay warm.