Though lichens vary widely in color and form, most often seen are the white crusty varieties that colonize the surface of trees, rocks and barren soil. A related disorder, lichen planus, more often affects the skin and inside of the mouth but can also affect genital membranes, where it can be more challenging to treat than lichen sclerosus. Lichen planus generally has broader targets, but an erosive form can affect the anal-genital region and other body parts and be as destructive as lichen sclerosus. In addition to pain, both conditions can cause intense itching that, lacking an accurate diagnosis, patients may mistreat with creams and other substances that only make matters worse.