Box dye refers to any and all hair color you can buy without a professional license. Yes you read that correctly. Everything from grocery store hair dye kits to beauty supply chain tubes of color are considered box dye. If you can buy it yourself, you really shouldn't use it on yourself.

Box dyes often contain high levels of ammonia and other harsh chemicals that can strip the hair of its natural oils and cause dryness and breakage. These dyes can also cause uneven color or damage if applied incorrectly or left on for too long.

Covering your gray hair at home is simple in theory — you select the correct color of boxed hair dye, apply and voilà. But even if you do everything right, you may be left with some stubborn gray hairs that end up showing through the dye.