How often can i use Redken EQ

You can use shades eq as often as needed. It is an acidic demi, which means that it doesn't damage hair, at all. It fades off slowly so you don't have to worry about build up. But I would recommend using any color more often  then every 3 weeks. I have some clients who come in every three weeks for a root touch up (bleach blondes) and I refresh their blonde all over with shades eq very appt. It is also great for keeping red hair vibrant! HTH!