Hello,

Thanks for posting your query,
I am pleased to be able to assist you answer your query.
From your description, it seems you have contracted an infection (not necessarily true kissing). It might be due to a viral infection or fungi (2nd option is most likely) or an indication/symptom of an autoimmune disorder. Usually these factors (infection, autoimmune diseases lead to increased melanin production).
The hyperpigmentation (darkening of lips) may be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris. People with darker Asian, Mediterranean, or African skin tones are also more prone to hyperpigmentation, especially if they have excess sun exposure.
If you have recently been on any medications or drugs (then you should get that checked out by your doctor) as certain hormonal therapies could also lead to that.
You might be having Peutz-Jeghers syndrome (an autosomal dominant disorder characterized by hyperpigmented macules on the lips and oral mucosa and gastrointestinal polyps). Mercury poisoning is another possibility (i.e if you had applied any mercury containing lotion on your lips).

Hope this was helpful information and let me know if you have any other information you want to share that can help me narrow down the different possibilities to just a few.

Dr. Bernard

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Thanks for updating,
It looks like the source of your dark lips is as a result of an infection (viral likely) or an allergy and the dark spots are simply a scar left behind after the infection has passed.
Other causes will have to be detected and ruled out by a dermatologist. Some possible causes could be herpes, cheilitis etc.
Time will do away with the scars naturally or you consult the dermatologist to provide you treatment for the scars/hyperpigmentation.

Hope this further helps
Dr. Bernard

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