The body produces a type of protein called IgE in response to an allergen, which binds with the molecules of the allergen. This binding leads to the release of histamines, the chemicals responsible for allergic symptoms, such as itchy eyes and runny nose. In most cases, these symptoms are self-limiting or easily treated and typically respond well to antihistamines such as diphenhydramine. However, allergies are not just a nuisance for some people: up to 5 percent of Americans have experienced severe allergic reactions, known as anaphylaxis. Anaphylaxis is a potentially life-threatening condition that must be treated immediately in order to minimize the chances of a fatal reaction. Common symptoms of anaphylaxis include shortness of breath, trouble swallowing (dysphagia), wheezing, itchy lips or mouth, nausea, vomiting, diarrhea, dizziness, and cramps. These symptoms indicate a serious allergic reaction. If symptoms affect more than one part of the body or system, such as difficulty breathing and a skin rash, the allergic reaction is most likely anaphylaxis or is heading toward anaphylaxis. Even if an allergic reaction produces manageable symptoms, such as a localized rash or watery eyes, within 30 minutes, it is possible that more serious signs may appear. Therefore, it is imperative to take immediate action when experiencing allergic symptoms, especially if they are new or the individual has experienced anaphylaxis before. Furthermore, about 20 percent of people experience a second, stronger anaphylactic reaction within 12 hours of the initial one; this is known as biphasic anaphylaxis.