hello i have gone through your query. yes your numbness of the lip is mostly due to cold sores.but the problem is why u r getting cold sores every couple of months.may be it is caused by the herpes simplex virus type 1, which is usually acquired in childhood through contact with infected saliva.it is activated by stress, anxiety, a cold or excessive exposure to the sun.unfortunately you can t cure cold sores permanently, and they like to keep coming back.but you can get yourself relief from it in certain ways.apply oragel on the affected area.change your toothbrush as it harbours the virus.if pain is more aspirin or paracetamol cn be taken.cold sores may be triggered by stress. During stressful times, sucking on zinc lozenges can boost the immune system. hope this ans helps Regards Dr. shesh