In fact, studies say that oral sex can help develop immunity against PID the symptoms of which are like fever, pain in lower abdomen, painful urination, bleeding, etc. An analysis of the PID Evaluation and Clinical Health (PEACH) data suggests that among women who presented with signs and symptoms of pelvic inflammatory disease (PID), those who reported having oral sex were less likely to have endometriosis, a gynaecological condition where the inner lining of the uterus starts growing outside the uterine cavity over the ovaries, fallopian tubes or around the outer lining of the uterus. This usually results in painful bleeding and more such discomforts.
Studies suggest oral sex is one way to gain immunity against PID and endometriosis. The reason being antigen present in the lymphatic system helps develop immunity from PIDs. And lymphatic tissues are in abundance in the oropharynx (part of the mouth). Around 619 women who were clinically suspected with PID participated in the PEACH study to find if there is a link between oral sex, PIDs and endometriosis.
The study concluded that women who reported having oral sex were less likely to suffer from endometriosis or PIDs. This might be due to the protective immune response in the genital tracks due to the lymphatic tissues present in the oropharynx.