???? Bite

Bob got bitten by something on Friday evening. He was playing on the patio. I don't know what bit him and neither did he. He had five or six bites on his left leg. I put hydrocortisone on it and put him to bed.
Saturday afternoon, his leg was huge. I had no Benadryl in the house, so I gave him some Claritin and it did not help. We wound up going to urgent care (what they call walk-ins on the west coast) as it was in the afternoon and his pediatrician only has office hours until noon on Saturday. His right leg (the good one) measured 21 cm in circumference. His left leg measured 24 cm in circumference. His left leg was also hot and red, and he had a low-grade temperature (99.7) He started on steroids and antibiotics - steroids in case it was just a venom reaction and antibiotics in case it was cellulitis.
The swelling is now down significantly - he is down to 22.5 cm, but every single one of the bites has turned into a bruise. I am going to call the pediatricians office in the AM because I want to spray the patio. I will ask them if they have any idea what could have caused such a bite. I don't think it was a flying insect as the bites are only on one leg. I think it was something that crawls and it crawled up his leg.
Potty training is on hold for the time being. Despite the fact that I have been giving Bob acidophilus supplements, he has a bad case of diarrhea from the antibiotics. We started using Desitin prophylactically.

Bob does not seem to be in much pain. I showed him the FACES pain scale and he picked out the FACE for 4/10 pain. He then ran away and started jumping on his trampoline. If his leg really hurt him, I don't think he would jump on the trampoline like that.

My fear is that it may have been a small scorpion. The effects of a scorpion bite can last a couple of weeks. But scorpion bites are supposively very painful, and I think Bob would have known he was being bit repeatedly by a small painful creature. He has a high pain tolerance, but not that high of a pain tolerance.

I will keep everyone updated.