Hello, I noticed my guinea pigs were scratching a lot but they had no bald spots or scabs 3 weeks ago. So I bought some ivermectin paste, diluted it and gave them the correct dose. After the first dose, the scratching seemed to slow down but after the 2nd and now 3rd dose it seems to be back to normal again. When my ivermectin paste arrived the weather outside was -20 degrees celsius and it was left outside all day. Do you think since it froze it made the ivermectin ineffective? Also, while I was treating them for mites I didn't bleach their cage or anything, I just did regular cleaning. My guinea pigs are scratching again a lot but they have no patches of missing hair or scabs. Do you think it didn't work because the medicine froze or because I didn't bleach the cage? Should I buy another tube and try again? I am worried that the mites have gotten used to the ivermectin and it may not kill them. Thanks for any replies.