"Harlem" is written in free verse, having no established sense of meter or rhyme. Its lines vary in length and employ both indentations and italics in its form. All of these elements lend to the unpredictability of the poem, which is a central theme that Hughes develops. The poem also uses numerous hard stops at the ends of lines, using five question marks and two em dashes in just eleven lines. This forces the reader to confront these hard stops to mirror the experience of those who have had their "dream[s] deferred."
The speaker deviates from the expected syntax from the opening line. Typically, we would expect the adjective to precede the noun: a deferred dream. Yet this construction emphasizes that the focus is on the dream itself and that logic has been defied. This line is interrogative, inviting a more personal experience with the reader.
The next lines employs alliteration: Does it dry up. Each word in this line is only one syllable, and the overall effect is a barren existence that reflects the simile in the next line. Raisins used to be grapes, full of life and moisture. They once existed in a completely different form.
The sense of distaste intensifies in the next lines as the speaker compares the experience of having dreams deferred to a sore that festers, or is filled with infection and pus. It runs over with bitterness, unable to contain its response to contaminants. A few lines later, the speaker asks whether deferred dreams eventually "crust and sugar over." This imagery conveys the sense that people with deferred dreams may "put on a happy face" while hiding a much more sickly truth below the surface of contentment.
Finally, readers arrive at a statement. There is no question here: Having to face continually deferred dreams weighs people down "like a heavy load."
There is a duality in the closing question, set off in italics. We both celebrate and fear explosions. Sometimes they signal joy, such as annual firework displays. And at other times, they signal death, such as in war. The italics here are unexpected, which reflects the unpredictability of explosions and therefore of the effects of deferred dreams.