Definition: Anaphylactic shock is a severe allergic reaction that can result in life-threatening symptoms like difficulty breathing, swelling in the face, lips, tongue, throat, or nose, and shaking. It's caused by an immune system reaction to small foreign substances like dust mites, mold, grass pollen, nuts, fish, animal products, insect bites, or even food. Detailed definition: "Aphthous rash is a manifestation of a severe allergic reaction that can result in life-threatening symptoms like difficulty breathing, swelling in the face, lips, tongue, throat, or nose, and shaking."