Do you ever change skin care products and breakout? or is it just me?

I have been using Lancome for a long time – and of course, it is pretty pricey. So every now and then I say to myself that I want to spend less on skin care products. And sometimes I hear from some magazines / websites that brand names and drug store brands really don’t have much differences… However, everytime I switch to other brands, such as oil of olay, I break out after a couple of weeks – is this normal?