Allergens are substances that trigger the immune system and produce reaction (sudden allergy attacks or chronic allergies) in susceptible persons. These symptoms can range from anywhere between cold-like (sneezing, congestion, itching) to potentially fatal reactions such as anaphylaxis. Some of the most common allergens are dust (actually dust mites), pollens, peanuts, tree nuts, animal dander, insect stings and some foods. Most allergies can be controlled and managed by the use of OTC antihistamines, injections from a doctor, and simply avoiding known allergens as much as possible. It is advised that people who have severe allergies, especially allergies that can result in anaphylaxis (hyperlink) carry an Epi-pen with them for emergency use. This is a device that contains a dose of epinephrine that will reverse anaphylaxis long enough to seek medical treatment.