Hello. Thank you for writing to us
I suggest a possibility of Fixed Drug Eruption/ FDE as the reason behind the black patch on your
upper lip.
This type of drug reaction is fairly common to antibiotics like
sulpha drugs and presents as circumscribed dark patches on lips as well as other areas on body.
The reason this eruption is called as Fixed Drug Eruption is because the eruption would happen at the very same site every time the implicated drug is ingested.
Therefore, if you consume the implicated drug you are allergic to you will notice that the patches darken.
The patient would usually know the drug that causes it because the eruption happens soon after (within few hours) of ingestion of the implicated drug.
Since you know that you are allergic to sulpha group of drugs it is mandatory that you avoid these.
For existing patches I suggest that you use the same moderately potent
steroid that you previously used i.e fluocinolone acetonide, twice daily for 2-3 weeks.
Regards