<s>[INST] I was bitten by a horsefly 9 days ago.  I have a blister 1.1/2 in wide by almost 1/2" high. I have taken 2 days of flucloxacillin 500mg 4x a day. It was bright yellow to begin with but today is has turned a grey colour.  Is this the antibiotics working or is it acting as an incubator!  It's not painful apart from the odd twinge, the cellulitis has gone but the blister does not seem to be shrinking. I'm 67 and it's across the top of my foot. [/INST] Hello dear,Thank you for your contact to health care magic.I read and understand your concern. I am Dr Arun Tank answering your concern.No, it is towards the edge of healing.It is because that antibiotics you have taken is working. So that the infection is towards the healing end you are will be very clear with the blister.As this blister is very big in size it takes some time to heal. I advice you not to worry. Keep taking your drugs timely.Try to avoid injury to the blister. If it bursts than the nude skin expose to the atmosphere making it vulnerable to the infection.So keep the blister protected with shocks anf shoes covering.I will be happy to answer your further concern on bit.ly/DrArun.Thank you,Dr Arun TankInfectious diseases specialist,HCM </s>