Hello Dear. Since you say that you have been tested negative for STDs it could be Non-sexually acquired genital ulcers. Non-sexually acquired genital ulceration or NSGU refers to painful ulcers in the genital area. It is classified into two types: 1. acute reactive aphthous ulceration 2. acute recurrent aphthous ulceration. Non-sexually acquired genital ulceration affects mucosal surfaces and the adjacent skin. The ulcers often arise in association with oral aphthous ulcers, which are quite similar in appearance. 1. Reactive genital ulcers: Reactive genital ulcers follow an acute systemic illness, such as tonsillitis, an upper respiratory infection or diarrhoeal illness. They mainly affect the vulva of adolescent girls but may sometimes arise in adult women. The ulcers may be very painful and result in dysuria (pain passing urine) or prevent urination altogether (acute retention of urine) requiring admission to hospital and catheterisation. Local lymph nodes may be enlarged and tender. The ulcers resolve within a few weeks and rarely recur. 2. Recurrent genital ulcers: Recurrent aphthous genital ulcers are more common in females than in males. They may arise continuously, regularly, e.g. prior to menstruation each month, or infrequently. Although they tend to be smaller than the ulcers occurring in reactive genital ulceration, sometimes they are large and numerous. Some cases of recurrent aphthous genital ulceration appear to be provoked by a specific infection, most often Epstein-Barr virus. Some patients later prove to have Behçet disease or Crohn disease (they have genital Crohn disease). Cause: The cause of genital aphthous ulcers is not fully understood. They may arise as the result of excessive acquired or innate immune response. Investigations: Viral and bacterial swabs should be taken to rule out infectious causes of genital ulcers such as herpes simplex (genital herpes), syphilis and chancroid. Swabs are negative in NSGU. Further tests will be directed by the symptoms of the underlying illness but should include tests for infectious mononucleosis. Biopsy of the ulcer should include surrounding skin. Findings are nonspecific in NSGU. Treatment of NSGU Treatment of genital aphthous ulcers will depend on cause but may include: 1. Analgesia such as paracetamol, nonsteroidal anti-inflammatories or stronger pain killers 2. Topical anaesthetic ointment or jelly 3. Topical corticosteroid ointment or paste 4. Intralesional steroid injections 5. Oral steroids, e.g. prednis(ol)one 6. Antistaphylococcal antibiotics if secondarily infected 7. Prolonged course of doxycycline or erythromycin to prevent recurrences. Hope i have answered your question. Feel free to contact me if you have any more questions. I ll be glad to help you. All the best With warm regards Dr Sanjay Kini