In the laboratory tests , the doctor will take a nasal smear .
Smear will be examined microscopically for factors that may indicate a cause : increased numbers of eosinophils ( white blood cells ) , which indicates an allergic condition .
In the laboratory tests , the doctor will take a nasal smear and it will be examined microscopically for factors that may indicate a cause : increased numbers of eosinophils ( white blood cells ) , which indicates an allergic condition .