Allergy
They are called allergens. During a reaction, your immune system releases antibodies. These are proteins that deliver a message to cells: Stop that substance! The cells then send out histamine, which causes blood vessels to expand, and other chemicals, and these trigger the allergy symptoms.When you’re exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause allergy symptoms. Common allergy triggers include: Airborne allergens, such as pollen, animal dander, dust mites and mold.Late summer/early fall ragweed is the most common cause of fall allergies. Depending on where you live, ragweed-fueled fall allergies can start in August or September and continue through October and possibly November. Pollen grains are lightweight and spread easily, especially on windy days.For most allergic reactions, the initial symptoms begin to go away a few hours after the allergen is removed and should be nearly completely gone after 1-2 days. If the itchy rash that you have on your arms and hands is hives (which would indicate a classic allergic reaction), you should see these go away fairly soon.Allergies cause symptoms that happen all at once. Check how long the symptoms last: Cold symptoms generally last 7 to 10 days, whereas allergy symptoms continue with exposure to the allergen (symptom trigger). Allergy symptoms may get better or go away soon after elimination of allergen exposure.