You need not worry about that whitening in your skin kup. that is normal with H2O2. I was exposed to this fact when I was younger coz my mom used it like an antiseptic for cleaning my wounds. You know when your a kid you tend to bruise around a lot from being so darn hyper. So even though it stings a lot (on wounds) I got used to it. The formulation nowadays are quite lesser in concentration and also , around the time I was in HS the medical practitioners moved away from using H2O2 as a wound cleanser ( it shouldnt be used on open wounds) and advocated using Betadine instead which later got canned for op use only and use only Normal saline for open wounds.... now in my working years they've moved away from betadine ( still used in Operations though) and onto Chlorhexidine ( NOT for open wounds) as the antiseptic of choice.... okay back to the topic again....