I have the itching on a rather unpredictable time table. It is sometimes several times per day, or other times only several times per month. I have basically the same experience with the CeraVe Itch Relief product as you do with yours. About 2 to 5 minutes after I apply it, it starts giving me relief which lasts several hours. It's not foolproof, however, and on some rare occasions not even this product can handle the itch. I also sometimes use a prescription steroid cream, but I try to limit how often I resort to that. Sometimes that doesn't work either. Scratching works EVERY time if I do it hard enough, but then I;m left with a mess on my body for days or weeks. It's a frustrating situation.
CeraVe has several different creams and lotions, so if you ever decide to give this stuff a shot, make sure to get the "Itch Relief" formula. Best of luck!