Does chemical toxicity cause leukocytosis?

No, usually not: Leukocytosis is an abnormally high number of white blood cells in the blood, as measured on a blood test. Both viral and bacterial infections can sometimes cause high numbers of white blood cells (wbc's) or low numbers of wbc's (leukopenia). Unusual leukocytosis, not caused by an infection, can be due to a bone marrow problem such as an early stage of leukemia. A doctor can further evaluate.

Be careful: Even a cold shower can briefly double the leukocyte count. When it's relatively mild, especially if the cells have normal appearance under the microscope and the absolute counts are reasonable close to reference range, it's not worrisome. Each specific chemical toxicity tends to have its specific findings; "multiple chemical sensitivity" is a fad diagnosis -- self-diagnose at your own risk.