Are pre-made egg whites in the carton healthy?

My husband has been trying to eat healthier & lose weight. He's been doing a great job so far, and recently bought a cookbook specifically for losing weight while working out. The recipes call for A LOT of egg whites to the point that today alone, for his breakfast & snack, I used 16 eggs!! 😧 Anyway, I'm sick of buying dozens of eggs every couple of days & also feel bad wasting all the yokes. Are the egg whites that come in those milk-looking cartons safe and healthy to eat? I'm just afraid that there's other stuff in them or something. I think it'll save a lot of money, time, & effort if I just buy those cartons from now on. Thanks in advance for advice!