Allergies do not necessarily itch. Most allergy sufferers experience itch to varying degrees, but some allergy sufferers are locally allergic and the nerves in the allergic part are not sensitive, so they do not feel itchy. Itching is a manifestation of skin allergy. As the body is exposed to allergens, antibodies are produced and histamine, leukotrienes and 5-hydroxytryptamine, which are factors that tend to cause itchy skin, are released, followed by a skin metamorphosis. Allergies can involve multiple sites and can manifest as skin edema and rashes in addition to itching. There are many allergens, including drug allergens, food allergens, dust allergens, etc. Drug allergens such as penicillin, cephalosporins, etc.; food allergens such as seafood, peanuts, etc.; dust allergens such as dust mites, pollen, willow, animal hair, etc. Allergic people or patients who are already allergic should pay attention to avoid contact with or eating the above common allergic substances, and if necessary, allergen testing is required. It should be noted that in case of severe allergic reactions such as asthma, edema and breathing difficulties, it is necessary to seek medical attention promptly and not to delay the condition by using private medication.