Do you know the different between a heat rash and something more serious?

Recently my sister-in-law called in a panic, because her one-year-old had been sent home from nursery with suspected chicken pox.

She was told not to return with the child until they had visited the doctor and got a doctor’s note or for a couple of weeks until the chickenpox had passed. After frantic work rescheduling and pulling in favours from family and friends, and a trip to the local GP it was found that my nephew had a heat rash and was perfectly fine to continue on at child care.

And despite said doctor’s note, the following week, the same thing happened again.

It made me wonder what is going on when an experienced child care worker can’t recognize the difference between a heat rash and chickenpox. Can anyone except highly trained medical practitioners know the difference?