Teagan's "catalyst" compares hurtful words to a chemical reaction that can't be reversed. Once the words are said, there's "no way back," and the speaker treats them as a spark that sets everything alight. The burning is "soul and body," so the damage isn't just a passing sting but something felt all through the person. What makes it worse is the isolation: "no one sees and no one hears." The pain is hidden, working "from the inside out."
The science language carries the poem's second half. "Half life" and "decay" suggest something slowly wearing down, and the speaker seems to hope the doubt might fade over time. But the question "forever?" hangs alone on its line, and the answer is bleak: it "seems to stay the same." The short lines, lack of capital letters and broken rhythm give the poem a tired, quiet feel. The mood is trapped and raw, a private hurt that refuses to shrink, with little sense of comfort or release by the end.