I have had the same experience with lichen sclerosus (LS). Rinsing with plain water after each urination helps, but for me cleansing after each urination with witch hazel on toilet paper (Tucks pads are too expensive) helps even more. I think that my genital area reacts against urine very strongly--perhaps even an autoimmune reaction.

The first symptom I had of LS was many years ago when I had a habit of urinating in unusual ways--outdoors, in the tub. But then I started having bad experiences--each time I would urinate not in a toilet, I would have symptoms the next day of what I called a "sweet" sensation that fluttered up my inner arms and on the soles of my feet. Very odd and unpleasant. Shortly thereafter, I was diagnosed with Hashimoto's thyroiditis. I was undergoing treatment at that time for infertility, and taking Clomid. I connected both the thyroiditis and the weird feelings on my arms and feet to some kind of strange physiological reaction to the hormones and hormone blockers I was taking. I believe now that it was also symptoms of LS.

Being careful to always cleanse with witch hazel or water after urinating, I keep the LS quiet.