Allergic reactions

• Reactions to food dyes are often known as food intolerance instead of allergies because they are not IgE reactions. There is no specific allergy test for Blue 1 or other food dyes. Some reactions to Blue 1 include eczema, hives, puffy eyelids, dry skin, sneezing, recurring ear infections, congestion and wheezing. Severe reactions include anaphylaxis.
  
  

Cancer

• According to an article by Laurel Curran at Food Safety News, "Evidence suggests, though does not prove, that Blue 1 ... causes cancer in animals."
  
  

Digestive upset

• Those who have an intolerance to Blue 1 may experience symptoms such as constipation, vomiting, bloating, abdominal discomfort and diarrhea. Symptoms can show up within hours or days of ingesting Blue 1. While a small amount of Blue 1 may cause no problems, eating an entire bag of candy with Blue 1 may trigger a reaction.
  
  

Other side effects

• Especially in those who have an intolerance, Blue 1 may affect behavior. Symptoms include headaches, migraines, anxiety, crying and fatigue. Blue 1 has also been linked to hyperactivity and behavior problems in children. According to the Feingold Association of the United States, Blue 1 can also cause chromosomal damage, which changes or breaks chromosomes of cells.