Symbolism, Imagery, Allegory
(Click the symbolism infographic to download.)
A thing that swells and itches, and after you scratch it, flakes. Sounds gruesome, right? So is sexual repression. Have you noticed how the ulcer seems to bother Winston most in the mornings? How about when its symptoms subside after he starts seeing Julia? Or how it becomes engorged again when Winston is separated from Julia? Exactly.