Technically, no. It is not possible to be allergic to sugar (sucrose) itself, however there are incidences of intolerance to sugars, such as lactose intolerance (the sugars found in milk and dairy products).
People often refer to ‘allergies’ and ‘intolerances’ to describe a reaction to food. They are often used interchangeably but it is important to note that they do not necessarily mean the same thing.
Food allergies and intolerances of any kind should only be diagnosed by properly trained medical staff. For more information on allergies or intolerance please seek advice from a health professional.