Food allergies are essentially immune reactions to certain proteins present in food. Medications used to treat allergies therefore target the chemical mediators of these immune reactions, such as histamine. Antihistaminic agents are useful for treating mild-to-moderate allergies. One of the most important medications used for severe allergies is adrenaline, which can save lives if administered in time.
Histamine is one of the major mediators of allergic reactions and is released from several of the body's immune cells in response to a food allergen (a protein or compound present in food). Histamine release can cause itchy skin rashes, wheezing, constriction of airways, and a red and runny nose and eyes. Some antihistamines used to treat allergic reactions to foods include cetirizine, levocetirizine, azelastine and loratadine.
Antihistaminic agents typically cause drowsiness and so driving and operating heavy machinery while taking them should be avoided. However, more recently developed agents such as promethazine have a less sedative effect than previous antihistamines.
Anaphylaxis or severe food allergy is a life threatening condition that typically leads to a severe fall in blood pressure due to blood vessel dilation and diminished oxygenation due to constriction of the airways. Blood vessel dilation also leads to swelling of the mucosal lining of the larynx (the entrance to the trachea) and may lead to choking and even death of the patient.
Adrenaline acts by narrowing the blood vessels and raising the blood pressure as well as by widening the airways to ease difficulty in breathing. Adrenaline needs to be administered immediately after detection of anaphylaxis.
People prone to anaphylaxis on exposure to certain foods may keep an auto-injector with prefilled adrenaline within easy reach. There are three types of auto-injectors including the EpiPen, the Anapen and the Jext. The injection of adrenalin is achieved by removing the safety cap and placing the injector against the outer thigh at a right angle and pressing down on the injector button for around 10 seconds. The injection can be administered through clothing to save time.
Reviewed by Sally Robertson, BSc