Pseudoallergy is a body's reaction that is similar to an allergic reaction, but does not involve the immune system. It is a direct reaction to the perpetrator (e.g., additives, dyes, preservatives in food), which triggers the release of histamine and other inflammatory substances from cells in the body. Symptoms of pseudoallergy can include hives, swelling, breathing difficulties, digestive problems, and in some cases anaphylactic shock. Because pseudoallergies do not involve antibodies, allergy tests usually do not show any reaction. Treatment usually involves avoiding triggers and using antihistamines to relieve symptoms.