I started having symptoms of LS when I was 23 years old (from what I can remember). It got progressively worse until I was finally diagnosed at 26. I did a ton of research and started seeing two alternative doctors about it. The symptoms gradually disappeared, and I have been symptom free for about 6 months. Based on all my research, it seems like the underlying cause varies from person to person, but I will briefly summarize what I believe were contributing factors in my case.
1.) Uncomfortable sex and/or sexual abuse. There is evidence that sexual abuse can cause LS, although I'm not sure if it causes or exacerbates the problem. Either way, my symptoms got a lot worse when I was in a relationship with a man who I was not very attracted to. My only advice (really, whether you have LS or not) is to not have sex if you have symptoms, or if you simply do not want to. The friction physically damages the skin.
2.) Underlying inflammation, which can be caused by the following factors:
a) infection. I had a bad one for a long time. At this point the LS symptoms were quite bad - lots of itching and pain, and shiny white patches. After getting a million tests done, I finally gave up on western doctors, went to see an alternative guy, and he gave me an anti-bacterial, anti-fungal, and anti-viral herb (it was a strong herb). The symptoms started to clear up immediately, and I mean by the next day. I suspect it was a fungal infection because symptoms worsened several months earlier when I was on a round of antibiotics (antibiotics alone will kill the bacteria that keeps fungus and yeast at bay, permitting fungal overgrowth). Anyways, that helped, but the symptoms were still not completely gone. There were other contributing factors...
b) Allergies. I got my alternative guy to test literally everything I ate on a regular basis, and it turned out I was sensitive or allergic to many foods. Dairy was the big one, and when I cut it out, I noticed the symptoms mostly disappeared. At that point, I was sometimes asymptomatic but sometimes it still flared up a bit, which still drove me crazy, so I pressed on.
c) Deficiencies. I had major deficiencies in iodine (this one was important.. I'll discuss it in my next point), vitamin E, zinc, vitamin B12, and I suspect several other things. I took supplements for a short period of time and majorly changed my diet. Now everything I eat is organic, and almost nothing is processed. I eat almost no restaurant food. Just a very natural diet - like how your grandmother would eat. It is a lot of work, but wow did it make a difference. The foods I noticed to be particularly helpful for LS are kale, swiss chard (both blanched to get rid of the oxalic acid), and bison/elk/organic beef. I also eat tons of yams and sweet potatoes. The pain and itching is completely gone. The only symptom I now have is mild follicalitis on one side which only comes up occasionally, and I'm not sure that is even related to the LS.
3.) One more thing. There seems to be a strong link between LS and hormones. As I said above, iodine was an important factor because I had subclinical hypothyroidism (this is very common). The problem is, when your thyroid gland isn't functioning properly, it throws your sex hormones out of whack. So if you are always tired and/or cold, then there is a good chance iodine supplementation might restore some hormonal balance. On top of the iodine, i also tried a couple herbs for hormone issues - black cohosh tea and raspberry leaf tea - and found they both seemed to help with the LS and other symptoms I had.
From all of this, if I could recommend anything, it would be this: first off, examine ALL your symptoms. Chances are, if there is something else going on, it is probably related and might give you a clue as to the underlying cause. Second, FIND AN ALTERNATIVE DOCTOR! The truth is, a western doctor cannot help you with this problem. I found that the naturopaths trained in North America were just as useless. The only two guys that I found who were able to help me had no formal credentials and practiced techniques that allowed them to 'get inside' my body and really figure out what was wrong. One did Muscle Response Testing and the other is simply able to 'feel' what is wrong when giving acupressure. Although these types of practitioners are less common in North America, I guarantee if you start asking around, you will find someone. If not, try going to some herb stores in your local Chinatown district, and they can often point you in the right direction.
I hope this helps! I was so hopeless when I first found out I had LS, but am now so happy I persevered in finding a solution. good luck to all who read this!