Allergies and angioedema can appear similar but have key differences. Allergies often cause sneezing, itchy eyes, and skin rashes, while angioedema results in sudden swelling beneath the skin, especially around the eyes, lips, or throat. Allergic reactions may be mild, whereas angioedema can be severe and life-threatening. In dogs, allergic responses may occur due to medications like cephalexin for dog infections. If swelling occurs after giving cephalexin, it could indicate angioedema. Always consult a vet immediately if your dog shows facial swelling or difficulty breathing, as prompt treatment is crucial for angioedema compared to mild allergic symptoms.