How is a sinus in front of the ear treated?

If a preauricular sinus does not cause any problems (such as recurrent swelling with pain and discharge) it may be left alone. However, as you say, if it is bothersome and gets repeatedly infected and requires antibiotic treatment each time, it is best to get it surgically removed. Surgical removal needs to be done carefully and the complete cyst under the sinus needs to be removed so as to avoid recurrence.