Did the results come back yet for the tests? I know tests cannot be fully accurate sometimes. When my son has something he is allergic/intolerant to little red bumps will form on his cheeks, then eventually will worsen and become dry, flaky, and when it gets really bad it oozes. What my son has is eczema, one of the reactions he'll get when he has any milk, soy, wheat, eggs, oats, barley, etc. Even in the tiniest amounts.
To rule it out has he had any new foods in the last month? Like bread or eggs, anything? Or has he been around any new pets?