When adding alcohol with eggnog it curdles?

Eggnog can curdle when alcohol is added due to the acidity of the alcohol, which can cause the proteins in the egg and cream to coagulate. This reaction is more likely to occur with high-proof spirits or if the eggnog is not sufficiently emulsified. To prevent curdling, it's best to slowly mix in the alcohol and use a well-blended eggnog base. Additionally, choosing lower-proof alcohols may help maintain a smoother texture.