My Daughter 8yrs old went ski-dooing on Jan 1st and got a fair sized frost bite on her shin. Since it has blistered and she keeps banging it. It is a little red around but not too bad. I have been putting polysporin on and keeping it covered during the day and letting it air at night. My question is how can I tell if it is infected and should I seek medical attention? Also how can I tell if the area is infected?

Frostbite treatment (http://www.essortment.com/all/frostbitetreatm_rwuh.htm)

I looked at a few sites concerning frostbite,it would seem the general opinion is if it blisters to seek medical attention.

Edit: any 'fair' sized injury/burn etc,should be seen by a doctor,unless you have medical training and know exactly what your doing.