4yr old has high level of eos %= 7.2%. rest of cbc is normal. has had allergies but never had high eos before. what are chances this is due to cancer?

Eosinophils: Highly unlikely this is cancerous. High eosinophils are seen in allergic children and in children with parasitic infections. It also is common to find this with normal lab variations. Repeat the test, have your doctor consider a stool test for parasites, and check an IGE antibody level. That comes from allergy but does not say to what. An allergist may help in that area.