I had this problem recently.  This put a damper on me and my husband's sex life for about 4 weeks, starting in mid April.  Just when I thought things were healing down there, it would "tear" again, making sex painful.  We kept trying, we were successful sometimes, sometimes not, because of the pain.  Imagine a paper cut or two right at the opening of your vagina.  Now imagine it having to stretch, and imagine some certain liquids burning it!  Ooooouch!!!  Absolutely unbearable.  You do not want this to happen to you.  Here's what I did that caused it, and things I did to make it better.

CAUSES:

• I used public restroom toilet paper, and I wiped carelessly and kind of roughly with it.
• During my period, I used pads with color in the middle.  A website said that that can irritate your skin down there, causing vaginal fissures.
• What STARTED MY VAGINAL FISSURES was using a very harsh soap with fragrance!  It ruined my natural pH balance!  I knew better, too, but I still reached for the soap.  Shame on me.
• Using that soap also caused a mild yeast infection, which can be a cause of vaginal fissures.
• More causes and explanations:  http://www.womenshealthmatters.ca/health-resources/health-information/resources/feature-article/preventing-vaginal-fissures-(womens-health-matters-article)
• Even more info:  http://www.wisegeek.com/what-are-vaginal-fissures.htm

CURES:

• I bought little travel-sized Kleenex tissues and put them in my purse for public restroom visits.  No more cheap, rough TP coming in contact with my nether regions!  If I run out of Kleenex, I just drip dry!
• I'm wiping more gently and carefully now.
• No more colored pads for me.
• No more using soap down there!  Not even gentle soap.  From what I have been reading these last couple months is that the best and most preferred cleaning method for the vaginal area is just WATER and your HAND.  This is advice from the experts.
• Cutting out ALL sugar, taking Vitamin C and probiotics helped cure my yeast infection very quickly.  But if you feel more comfortable seeing your doctor or getting over-the-counter medication, that works too.
• Finally, using a water-based lubricant like my husband and I always do helps tremendously! 

I hope this helps everyone prevent this condition!  It is not fun.  It hurts like heck and it is so frustrating as it takes a long time to heal...especially if you are sexually active with your partner, it can go from healing, then it tears again, then heals, then tears again!