Which of the following is a common symptom of food allergies?

Nausea and vomiting are indeed common symptoms of food allergies, as they occur when the immune system reacts negatively to certain food proteins. When a person with a food allergy consumes a trigger food, their body may release histamines and other chemicals, leading to a range of gastrointestinal symptoms. This immune response can manifest quickly after ingestion and includes not only nausea and vomiting but also stomach pain and diarrhea.

In terms of the other options, increased appetite is not typically associated with food allergies; in fact, individuals often experience the opposite reaction due to nausea. Improved digestion would not be a symptom of food allergies since the digestive system often faces challenges when a food allergen is present. Excessive fatigue may occur in individuals dealing with food allergies but is generally less immediate and directly linked when compared to symptoms like nausea and vomiting.