DS is constantly getting bitten. He's covered in bite marks all of the time for about a month or more (definitely getting bitten as far back as Feb half term).
They appear both during the day and during the night.
No one else is getting bitten.
I've checked his bed and there's no evidence of bed bugs or fleas.
I've washed everything.
We hoover and clean. The house isn't cluttered.
I've sprayed the house with Indorex and raid despite seeing no evidence of bugs/fleas.
I've had to give him antihistamine on a few occasions because they've been so bad.
So... what is it? What more can I do?