— Victoria, Virginia Swelling or angioedema of the tongue must always be taken seriously because if the swelling spreads back in the throat, it can interfere with or even entirely obstruct the airway. Also, some swelling progresses very rapidly (sometimes within minutes), although that is not always the case. There are different things that can trigger swelling of the tongue. In children, a food allergy, medication allergy (including over-the-counter medications for fever and headache like aspirin or ibuprofen), or an inherited condition called hereditary angioedema should be considered. In adults, the same list applies; additional causes include medications (especially ACE inhibitors for high blood pressure) and other swelling problems, such as acquired angioedema and idiopathic angioedema, or a newly described condition known as hereditary angioedema with normal C1 inhibitor (more about testing for these below). The hereditary conditions run in families, so asking relatives on both sides if they ever had problems with sudden swelling would be useful. Unusual causes for swelling of the tongue include infection, trauma, or an insect sting, although these are usually relatively obvious. When tongue swelling is caused by a food allergy (which is not that common), there are usually other symptoms that accompany it, such as itching, hives, facial swelling, wheezing, vomiting, and others. Tongue swelling should be treated with an injection of epinephrine (the treatment for a severe allergic reaction) if the tongue is constricting the airway. Epinephrine will not work if the cause is not allergic, however. If the swelling is less severe, it is usually treated with antihistamines and corticosteroids. These medications are typically continued for a few days, until the episode resolves. Anyone with tongue swelling (especially before the cause has been determined) should be given a prescription for an epinephrine self-injector pen (the two available brands are Epipen and Twinject) and taught how to use it. Make sure that you and your daughter understand how to use the self-injector pen and use a practice pen several times, so that if you ever need the real thing, you will not fumble around or use it incorrectly. The next step is trying to figure out the cause of the tongue swelling, because that is the best way to prevent it from happening again. Foods, drinks, candies, and medications taken in the few hours before the onset of swelling should be reviewed. Any trauma to the mouth or dental work can trigger attacks of hereditary angioedema, so events just before the onset of swelling should also be reviewed. Allergies to medicines are simply treated by stopping the medication and labeling your daughter’s medical record sufficiently to make sure she never receives the culprit drug again. If the cause is unclear, however, then an allergist should evaluate your daughter, as this is one of the conditions that allergists specialize in. It would be very helpful if the doctors in the emergency department had tested your daughter’s complement 4 (or C4) level at the time she had symptoms. This test screens for problems caused by abnormalities in blood proteins, called complement proteins, which control inflammation in our bodies. If C4 was not checked at that time, then please ask your primary care clinician to check a C4 level, a C1 inhibitor antigenic level, and a C1q level, even before you see the allergist. A low value in any of these tests suggests a disorder of the complement proteins, and this is helpful to know when performing further tests to determine the precise problem.