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This type of antibiotic is not usually helpful for the type of organism that causes this problem. Metronidazole or Flagyl is used for protozoal and anerobic infections (infections common in the intestinal tract and the STD trichinomias). In fact any type of antibiotics will not treat this condition well, because "antibiotics have difficulty penetrating the outer wall of the abcess".
This is a sebaceous gland that has become clogged - similar to what happens when a blackhead forms on the face, except more extensive. The natural secretions harden in the pore causing more build up behind it. The fluid is made sebum, blood and lymph fluid. This is a type of abcess called a boil. It is not uncommon for them to occur repetatively, especially if not treated completely - which often means lancing. (Informational: In rare cases these can develop, come and go and spread, usually near the arm pits, groin, and anus until scarring develops. When this occurs the condition is called hidradenditis suppurative. There is no indication that this condition will occur with you, but be extra careful when handling any drainage and disposing of it to decrease the likelyhood of spreading)
Warm compresses (cloth and salt water) are applied up to 3 times per day in order to help the boil come to "a head." After it begin to drain, and the warm compresses should be continued to keep it open until it is finished draining.
Long term preventative care: when steaming up in the shower, the pores will open, and at that time it is good to scrub any skin pore areas you have that may be prone to blockage. An exfoliation sponge is a good tool to use, although a rough washcloth will help some.
So, applying moist warm compress three times per day would be recommended at this time to help it open and drain.
If the boil does not come to a head on its own then incision and drainage is often required. This is of course only performed by a physician under sterile techniques, as it is a minor surgical procedurer. Currently ou will want to try the warm soaking procedure for a week or two before that decision is made. When the boils start to drain, if you are very, very careful, you can gently compress around the edges of the boil to help expel some of the pus (from the outside towards the inside drainage opening). if you do this, you must be very careful not to press the infection deeper into the tissues - if you there is any chance of this occurring do not express the pus, leave that to the doctor if it does not come out on its own from the soaking (it could cause deeper infection and tracts to develop in the tissue). When drainage begins you will want to cover with a gauze dressing during the day. You may place antibiotic ointment over the opening of the boil before applying the gauze. It is important to change and dispose of the gauze dressing after each soaking or later at least daily and to not allow anyone or yourself to touch it is - in case of an easily spread bacteria. You should be careful not to spread the bacteria onto other parts of your skin either. Also, always wear cotton loose fitting shirts, so that the area remains as clean and dry as possible.
Very careful handwashing is needed all the time to prevent spreading the boil. Try to keep the pus off the skin when it comes out (if it is draining profusely at first, change the dressing frequently). When it is drying up and healing, remember to continue washing the area with mild soap and water 2 times daily and continuing to wear clothing that allows air to the area. This may help prevent further occurrences.
In severe cases, such as in multiple boils or hidradenditis suppurative, surgery, photodynamic therapy, radiation therapy, antibiotics, hormones, immunosuppresents, retinoids and corticosteriods may be tried. Home therapy is still warm compresses with either sodium chloride (salt water) or Burrow's solution.