What does a rash from a shellfish allergy look like?

Hives, usually. Most rash from shellfish allergy looks like hives (urticaria) and/or swelling of the eyes, lips and hands (angioedema). A few people with atopic eczema who are shellfish sensitive might get worsening of their eczema. People who process shellfish (like fishermen or cannery workers) might get an eczema-like rash on their hands and skin where they contact the shellfish.
Usually hives. The most common rash associated with shellfish allergy is urticaria, or hives.