Oh I just love this liniment! I usually use this for headaches caused by stiff neck. Mine can get pretty nasty and can last for days. I don't get relief if I don't rub my neck and temples with Pau d Arco.
Its made up of methyl salicylate, camphor and menthol, but has a nice sweet smell that is actually very refreshing. When I apply it, the menthol seems to seep through deep in my tissues to separate the knotted parts. It seems that I can feel it working through my muscles and giving me a massage. I can then sleep immediately, as the sensations would lull me to sleep.
It is actually pretty cheap at about $2.25 per 60 ml bottle and it lasts a long long time. We use it for other aches and pains and insect bites but for me, I like it more for my neck and head. I feel greasy using it on my back.