Contact dermatitis on the face Contact dermatitis on the face Contact dermatitis usually affects areas of skin directly exposed to an offending substance. Here, the dry, red rash is likely caused by cosmetics or soap. Poison ivy blisters Poison ivy blisters Blisters such as these are common in a skin reaction to urushiol, the highly allergenic oily substance in poison ivy. In a latex allergy, your immune system identifies latex as a harmful substance and triggers certain antibodies to fight it off. The next time you're exposed to latex, these antibodies tell your immune system to release histamine and other chemicals into your bloodstream, producing a range of allergy signs and symptoms.