The allergy is triggered by a protein in the latex. Someone can use these gloves for years and then suddenly develop an allergy. This means that they could then get a reaction whenever they touch rubber. In extreme cases, the person can react so strongly that they fall unconscious. High quality gloves are processed to reduce the levels of protein.
Cheaper gloves are usually a greater danger.
Manufacturers should be asked to give information on the levels of free protein in their products. Powdered latex gloves are by far the most dangerous. They contain corn starch which binds to the protein making it more easily absorbed. Also the dust, if breathed in, can cause asthma. Disposable latex gloves should only be used as a temporary barrier against infection as oils and solvents quickly weaken them.