Something seems off here (not necessarily with you, but with the daycare). Is this a professional daycare, like a business that is only for the care of infants and toddlers, or is this a daycare in someone's home, where a mom earns some money by taking in a limited number of kids to watch during the day? Did he take the Claritin at home or at the daycare (or both)?
Is the daycare licensed?
I cannot imagine, under any circumstances, caring for a 2 year old who goes limp, is unresponsive, and couldn't be woken up, and then not immediately calling 911. Who takes a baby or toddler outside to wake them up after a medical episode? Sure, when you have sleepy toddlers who want to lie down and just watch tv, you might say "let's go outside and get some fresh air and wiggle a little!" But that's never the response when a toddler has gone limp and unresponsive, or a child has experienced a possible head injury.
Right now, it seems like this is a bigger problem than the Claritin. What are their emergency procedures? Who made the decision to try and revive an unconscious child by taking him outside?
I would get this child to a doctor immediately, and bring the Claritin bottle with you, and make a note of how much he took and whether he was given any Claritin at the daycare, and I'd get a new daycare place. Today.
And this may need to be reported, to whomever licenses daycare in your area. That was a serious mistake that they made. If it's a national chain, call the headquarters. Ask the doctor or nurse for advice.