[header] How to spot contact dermatitis symptoms [title] Beware of sudden rashes. [step] Contact dermatitis usually shows up when you've been touched by a substance that triggers a reaction, like poison ivy or oak or latex gloves. The rash usually will crop up suddenly, within hours of contact. 
It may also last for two to four weeks. [substeps] There are two basic kinds of contact dermatitis, allergic or irritant.