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It seems to be allergic reaction to steroids. You should stop either or both to see if stopping them will not cause lip swelling or not. If so, they are the cause. If not, the cause is due to different one.
Are they prescription or over-the-counter? Did you start to take new batch of them just before your symptom started? Are you aware of anything which might have triggered it? Any medical problems? Any recent medications just before your symptom started? Any allergies? Any family medical history?