How can I protect my teeth properly after purging/vomiting?

Do not brush them! Brushing your teeth after vomiting spreads your stomach acid more an increases the speed at which your teeth decay from said acid. I would suggest, if you have thrown up, to rinse with water and then mouthwash. The water will help clean out and left over bits, as well as some of the stomach acid, and the mouthwash will help kill bacteria that entered your mouth, via throwing up, as well as freshen your breath.

Unfortunately the acid from purging and vomiting can do long-term serious damage to your teeth even if you do your best to take care of it. The best way that you can help to minimise the damage is to brush your teeth after vomiting, use mouthwashes and book in for regular cleans with your dentist.

Eating disorders like bulimia, anorexia nervosa, and binge eating affect not only your general health but also your oral health. A few of the common issues related to these disorders are acid erosion of the surface of the teeth, dry mouth (xerostomia), and tooth decay (caries). A few ways to protect your teeth from erosion are to rinse your mouth out with water or a fluoride mouthwash after vomiting, to avoid brushing your teeth for an hour to prevent the residual acid from eroding your teeth, and to be sure to brush and floss at least twice daily. I hope this is helpful for you!