Are psoriasis and allergies linked? The immune system appears to play a key role in both. Researchers have found that people with psoriasis are more likely to have a greater number of inflammatory mast cells (see left) the kind that trigger allergic reactions, such as swelling and itching — than people without it. Although psoriasis may be a reaction of the immune system, it is not proven to be an allergic reaction. Studies have found no link between allergens and psoriasis.