I absolutely love most synthetic clothing items, but I still carry at least one cotton bandanna, preferably red (unbiased research shows red to be a much more effective color than , say, blue). The virtue of the cotton bandanna is its versatility - it can strain large impurities out of a water source, then function as headgear to cool down my noggin in hot weather. I often use mine as a hot pad when cooking. I clean my glasses with it (at least early on during the trip, before it has seen too much use as a water strainer). It's an arm sling, it's a bandage, it's a trail marker. It's incredibly versatile! and they are very cheap. But wait, there's more..Some kinds even come with knot diagrams, maps, and other useful tidbits of outdoor lore. End of Ronco commercial.