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The only cause of vaginal entrance bumps that is left are Bartholin cysts, if all others like STDs and genital herpes have been excluded.
A Bartholin's cyst causes swelling of the labia on one side, near the entrance to the vagina.
They are formed as a result of blocked pores of the Bartholin glands which are present normally on the entrance of the vagina and their function is to secrete fluid onto the mucosal (inner) surface of the labia-the lip like skin surrounding the vagina.
When blocked the secretions accumulate inside the glands and they swell forming cysts that can felt as painless bumps on the entrance of the vagina.
They become painful when infected secondarily by a bacteria or STDs, An abscess occurs when a cyst becomes infected. A Bartholin cyst abscess demands an Incision and Drainage with antibiotics if required and preferred by the doctor as a treatment.
The ultimate definitive treatment of these cysts is surgical, called marsupilization, if they are not infected.
This is usually done in an outpatient surgical setting.
It is addvised that you see a OBS/GYN doctor for these cysts if viral etiology like Herpes has been ruled out or if they start bothering you or become red, hot and swollen.