Causes for body temp of 95.5 F?

My older brother was recently bitten by ticks and as a result the area has become red and inflamed. He checked his temperature to see if he was running a fever, the thermometer said it was 97 degrees F. He normally runs in the 96.5 range so this for him was a slight fever. The next day (earlier tonight) he checked his temp again and found it had dropped down to 95.5 degrees F. My question is what could be causing the possible low body temp? Lyme disease would make him run a fever, which is the opposite. I'm guessing it could be stress, but am wondering if there are any other causes that he needs to be checking for. It's summer time and he didnt eat anything cold before taking his temp. In fact he just finished eating fajitas and peppers. Thanks.