How soon can you have sex after you tighten your vagina with alum?

Firstly, you should never use alum in the vagina; it irritates the lining of the vagina, and can scar it.

However, to answer your question, you could have sex about an hour after using the substance. However, if you wait until the following day, your vagina will be back to its normal size - alum doesn't help this, it's a myth.

The only way to make your vagina small again is to abstain from sex for at least a year. It will tighten inside and around the entrance during this time, though most women don't wish to use this method.

Some women who have cheated on their regular partner use alum to try to tighten the vagina so that he does not realise his partner has been unfaithful.  To be honest though, there is very little chance that he will notice a difference.

The best course of action, short of abstinence, is to do Kegel exercises regularly. This tightens the pelvic floor and helps maintain the elasticity of the vagina.

To do these exercises you really just have to use the same muscles that you would if you were stopping a flow of urine half way through. Hold like that for 3 seconds, relax and then do it again - keep this up for 15 minutes, twice a day.