What are common symptoms of an allergic reaction?

The symptoms of an allergic reaction most commonly include rash, itching, swelling, and difficulty breathing. These symptoms arise as the body's immune system overreacts to a substance, known as an allergen, which can be anything from pollen to certain foods. The rash and itching are usually a result of skin coming into contact with the allergen or the body's release of histamines, which cause inflammation. Swelling can occur in various parts of the body, particularly in the face, throat, or tongue, and difficulty breathing may be a sign of a more severe reaction known as anaphylaxis, which requires immediate medical attention.

Other options present symptoms that are not typically associated with allergic reactions. Headaches and nausea could result from various causes, including illnesses or migraines, and are not definitive indicators of an allergy. Similarly, fever and chills suggest an infection rather than an allergic response. Coughing and sneezing may occur in response to allergens like pollen or dust but are not comprehensive enough to define an allergic reaction, as they can also result from other respiratory conditions such as colds or flu. Therefore, the combination of symptoms listed in the correct choice accurately reflects a typical allergic reaction.