Hair chalk is safe for adults and kids. Most hair chalk formulas contain ingredients such as bentonite, calcium carbonate, mica, and pigment. All these ingredients are minimally toxic. However, it’s always best practice to do a patch test to ensure you’re not allergic or sensitive before applying it to your hair. In terms of overall hair health, hair chalk is safe to alter your hair color occasionally temporarily. While it’s not as damaging as bleaching and using permanent hair dye, the chalk can suck some of the moisture out of your hair. After washing out the chalk, it’s essential to follow up with a deep conditioner or a hair mask to restore your hair’s moisture balance and avoid damage.