History and tests. Unfortuneatly the current available skin and blood tests can too frequently test negative when latex allergy is present. These tests are useful if positive in demonstrating allergy. A history of rashes where latex touches you, trouble beating, hives, anaphylaxis (trouble breathing, dizziness or passing out) with exposure suggests latex allergy. Patch testing can help with a rash with latex.
Allergy test. Some allergist may have skin test available for latex allergy. But the reagent is very hard to get in us. There is a blood test that your doctor can order, ige to latex, which can help you finding out the answer.