Read the ingredients on a typical brand of dry shampoo, and you might see some ingredients you previously thought you would only need to light a barbecue, like propane and butane. This is a little alarming, as you're spraying these chemicals directly onto your skin and perhaps even breathing them in.
However, the Cosmetic Ingredient Review Panel confirmed that butane and propane are safe in shampoo, as they vaporize very quickly and are only used in small amounts.
Dr. Alan Bauman, board-certified hair restoration physician, confirms that the propane is nothing to worry about, although too much dry shampoo can leave hair dry if the hair isn't getting enough natural oil.
If you use dry shampoo routinely, you may want to rethink the amount of exposure you're getting to these chemicals, even if the risk is very small. Having the product sit on the scalp for long periods of time increases the likeliness of the chemicals absorbing into the skin, which can cause irritation.
To avoid these potential risks, opt for a brand that boasts more natural ingredients, or perhaps even consider making your own dry shampoo at home. Dr. Bauman also suggests to make sure to wash your hair regularly with shampoo and conditioner so the powder does not build up on your scalp, limiting your dry shampoo use to about one to two times between washes.
Your current dry shampoo is harmless if you're using sparingly, although it might be worthwhile to avoid the brands containing chemicals until more is known about the effects. In the meantime, stay away from open flame to avoid any "Michael Jackson Pepsi commercial" drama and check your bottle for hazardous ingredients before causing an unnecessary scene in airport security.