I've read many contradicting things while surfing the web. Some people say that your skin can get used to a cleanser and that it's important to rotate your cleanser every couple of weeks or so. Other people say that the only product that can lose its effects over a while are topical antibiotics., and that if you rotate cleansers then your skin will freak out from using too many products. I just switched to a new cleanser, and it's been working wonders, as opposed to my old cleanser which was too harsh. I am very worried that this will lose its effects, is it necessary to rotate with another cleanser?
Your cleanser may lose effectiveness for a few reasons:
1. Antibacterial ingredients which P. acnes bacteria can "get used" to, like triclosan (exceptions: BP, sodium sulfacetamide)
2. Active ingredients are degrading, due to age and/or improper storage conditions
3. Formulation flaws, like weak or no preservatives
The skin only "builds up a tolerance" to some topicals when it comes to irritation, like retinoids. But after the irritation stops, the effectiveness will pretty much still remain the same.
The other thing about cleansers is that many use different surfactant ingredients. Some types of dirt, makeup, or whatever may be cleaned off better by a different type of surfactant. Personally I see this applies more to hair. For example, if you use a conditioner with a lot of dimethicone in it, you need a sulfate shampoo to prevent the dimethicone from building up. So someone who uses a sulfate-free shampoo and a conditioner with dimethicone, will need to rotate in a sulfate shampoo every once in a while.
I wouldn't worry about rotating your cleanser for the surfactant reason unless you use a lot of makeup or work in grimy conditions.