When used on its own, the In2mate moisturiser should not curdle. However if you use the In2mate moisturiser at the same time as the In2mate Lubricant, then sometimes curdling occurs as they are two completely different formulations (one for internal use and one for external use) which do not mix together easily. If curdling does occur, there's no detrimental effect, its just a cosmetic issue.  The two products are not designed to be used at the same time. However if you want to use them together leave 15-20 minutes after applying the In2mate moisturiser before using the In2mate lubricant to allow for the moisturiser to fully absorb into the skin.