According to the MayoClinic, food allergies affect 6 to 8 percent of children under 5 in the United States and 3 to 4 percent of adults. Food allergies can cause a range of symptoms from abdominal pain to hives. Symptoms may come on suddenly after eating a specific food or gradually, affecting one part of the body or several at a time. Food allergies can cause itching and redness all over the body including the hands.Food allergies are caused by an immune response in the body triggered in response to foods that the body misunderstands as a threat. No matter the amount, once the offending food is ingested, antibodies and histamine are released into the blood to repel the substance. When this occurs, you may experience digestive upset and skin allergy symptoms. In some people, food allergies can trigger a severe reaction called anaphylaxis, which is life threatening.The release of histamine in the blood stream affects the digestive system and the skin. Symptoms of skin allergy are tingling or itching in the mouth; hives; itching; eczema; swelling of the lips, face, tongue and throat; wheezing; abdominal pain; diarrhea; congestion; vomiting and dizziness or fainting. Symptoms of the severe allergic reaction anaphylaxis are rapid pulse, shock, dizziness, difficulty breathing and loss of consciousness.Most food allergies are caused by foods such as shellfish, peanuts, fish, eggs, milk and wheat. Food allergies are caused by the lack of an enzyme needed to digest a food, food poisoning, sensitivity to food additives, recurring stress and Celiac disease. Risk factors for developing food allergies are a family history of food allergies, having food allergies as a child, age and asthma.If your hands are itchy and red after eating a specific food, make a note of the food and any other symptoms you may be experiencing and contact your physician. Itchy skin on any part of the body can be treated by using over-the-counter antihistamines. MayoClinic states that over-the-counter antihistamines are for the treatment of minor allergic reactions not for severe reactions, which require immediate emergency care.