Flanelette (sp?) sheets

I was talking to my grandma the other day and she told me not to get flanelette sheets for J, or ourselves for that matter. She said it will affect our asthma (how lucky - we all have it ! )

I haven't heard of this - anyone else?

(J is alseep in some Flanelette pj's but he doesn't sleep under a blanket or anything... I want to try and make it a bit warmer for him.)

Thanks!