Whether it is safe to wash your hair everyday depends on different people and hair type. For people who have oily hair, it is good to wash their hair daily to avoid buildup of oils in it. However, some people have dry hairs that require to be lubricated. Washing such hairs daily would strip of their natural oils thus causing them to weaken and break up. If you wash your hair daily, make sure to use mild shampoo.
I wash mine every day, sometimes multiple times a day if I'm sweating in the barns or putting up hay. I suppose it depends on your individual hair type, but my hair looks healthy and is shiny and bouncy, lol! It's a lot better to wash out sweat and dirt than it is to leave it on your scalp and hair.