I wouldn't use it anymore. Caused a huge ulcer on my penis from overdoing it
Yes, its perfectly normal for them to turn white! 1) its confirming that indeed they are GW. 2) Its killing the warts. So even though it is painful and only if you want to continue using this method ( which I have heard can be effective) I would continue applying ACV either at night or for small periods during the day ( Basically the length you can handle the pain) I would recommend applying Vaseline to the good skin to avoid burning. - On another note, it is always wise to go to your local clinic to get treatment. But I know in some cases it can be embarrassing. But it is worth it.
Yes it is normal. They may not ever disappear from this home treatment. Go see a doctor (GYN or dermatologist) because all you are doing is harming the top layer skin and you should stop this.