Although the condition resembles others that are easily cured, doctors

Choice (A)'s use of "if" and the conditional "would" is redundant; one or the other would be enough.
Choice (E) has the same problem. Also, in choice (A), "consistently direct application" means something different than "consistent and direct application." The latter means that the application has to be direct AND occur regularly, while the former means that the application has to be direct every time it is applied, without any real indication of how often.
Choice (B) avoids both of the problems of (A) and correctly places "only" before the one way that a sufferer of keratosis pilaris might improve her symptoms. By putting "only" before "lotions and creams," (C) and (D) indicate that the one way symptoms may improve is if a sufferer uses nothing except these lotions and creams, which doesn't quite make sense since the sentence doesn't identify what would make these specific lotions and creams (and not others) helpful.

The correct answer is Choice (B).

• "Only" is a very tricky word to place in English: depending on where you put it in a sentence, it can dramatically change the meaning. We have to be extra careful with the usage of 'only'