Liquid diets are used for a variety of reasons. A clear liquid diet is commonly prescribed before surgery or if you are suffering from gastroenteritis. Alternatively, you may embark on a juice fast, or take a commercially prepared liquid diet to lose weight.There is no scientific evidence that a liquid diet causes itching; however, if you are allergic to an ingredient in the diet, you may develop hives.Potential allergens in liquid dietsThere is no food that is scientifically proven to be hypoallergenic, and people can develop an allergy to just about anything.However, some ingredients in liquid diets are more likely to be allergens than others. For example, dairy products, peanuts, tree nuts, fish, soy, wheat, shellfish and eggs are the foods most likely to cause allergies, according to the Mayo Clinic website.Check the ingredients of the liquid diet carefully to ensure that it doesn't contain an item that you are allergic to, especially if the liquid meals are commercially prepared.DiagnosisIf you are sure that an ingredient in the liquid diet is giving you hives but you aren't sure which ingredient is the problem, contact your physician. She may send you to an allergist for testing in addition to prescribing a different diet or meal plan.If the allergic reaction is severe, such as hives that occur everywhere on the body, swelling of the face or trouble breathing, discontinue the diet immediately and seek immediate medical attention. You may be experiencing a severe allergic reaction.TreatmentThere are strategies for preventing allergic reactions to foods. The first, and most important, strategy is to avoid the food that causes the reaction.If the food is a common ingredient, such as wheat, eggs or milk, consult a nutritionist or your physician for a meal plan that will help you avoid that ingredient.In addition, if your reaction is severe, you may need to avoid restaurants or places where that food is prepared or served. For example, some people with peanut allergies must avoid being around peanuts and peanut products.Alternatives to a liquid dietA liquid diet is rarely the only option, except in cases of severe gastrointestinal illness or surgery. Follow a sensible meal plan that focuses on healthy options and omits any foods to which you have allergies.If you have problems determining which foods are healthy for you or if you find healthy foods unpalatable, a nutritionist can help you create a plan that focuses on the healthy foods that you enjoy yet also provides adequate nutrition.