A humectant absorbs moisture and keeps a moisture balance in the hair and skin. Humectants will search for moisture in your own hair too. Therefore, in areas where it may be hot, but dry, these products may actually do more bad than good. In the right condition, humectants are materials used in products to moisturize dry or damaged hair.
Film forming humectants are excellent moisturizing ingredients that form a film over the hair and will help resist dehydration. These ingredients are safe to use in low dew points. (More info...)
These ingredients are either OK to use, or weren't an exact match for those to avoid.