Risk in Brief - Sudan Dyes in Food

Sudan Dyes in Food


  1. Sudan dyes are synthetic chemical dyes of similar chemical structure. They are aromatic compounds containing azo group ( - N=N - ).
  2. Sudan I, II, III and IV are kinds of the Sudan red dyes. They can be generally applied for colouring substances such as hydrocarbon solvents, oils, fats, waxes and plastics.
  3. Sudan II and III can also be used in cosmetics and drugs applied externally whereas Sudan IV (also known as scarlet red) can be used in veterinary and human medicine as an ointment or dressings for stimulating wound healing.
  4. In recent years, the adulterated use of Sudan dyes in food has attracted much concern. Following the discovery of Sudan I adulterated chilli products in France in May 2003, surveillance on food products contaminated with Sudan dyes have been conducted by food authorities worldwide.

Toxicity of Sudan Dyes

  1. Sudan I was considered by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1973 to be unsafe for use in food, on the basis of toxicological evidence.
  2. Although Sudan dyes have been reported as contact allergens and sensitisers, the greatest concern has been on their possible carcinogenicity.
  3. International Agency for Research on Cancer (IARC) conducted evaluation on Sudan dyes in 1975 and considered that Sudan I was carcinogenic in mice following its subcutaneous administration, producing tumours of the liver and that it also produced bladder tumours in mice following its implantation into the urinary bladder.
  4. In its subsequent evaluation in 1987, IARC considered that there was no adequate data for carcinogenicity in humans and limited evidence in experimental animals for Sudan I and II, and inadequate evidence in experimental animals for Sudan III and IV. IARC considered that Sudan I, II, III, IV were unclassifiable as to their carcinogenicity to humans (Group 3).
  5. In recent years, concerns on the genotoxic potentials of Sudan dyes have been raised. Several national bodies and food authorities consider Sudan dyes as genotoxic carcinogens while others regard these Sudan dyes as possible carcinogens.


  1. In Hong Kong, Sudan dyes are non-permitted colouring matters in food under the Colouring Matter in Food Regulations made under the Public Health and Municipal Services (Cap.132).
  2. Sudan dyes are also not approved for use as colouring matters in food in Mainland China, and in countries including the European Union, Australia and Canada.

Advice to the Trade

  1. Source food supplies from reliable suppliers. Do not accept food from dubious sources.
  2. Put in place a system to monitor the incoming materials. Record and check thoroughly all food supplies at the receiving end.
  3. Conduct quality audit to incoming materials and end products, which is particularly important for manufacturers to ensure that ingredients they use (e.g. chilli products) do not contain any Sudan dyes and to conduct laboratory analysis if necessary.
  4. Maintain a good recording system to facilitate back-tracing and recall, if necessary, in case an incident related to their food happens.

Advice to the Public

  1. Purchase food from reliable retailers and caterers.
  2. When shopping for foods, read carefully information on labels.
  3. When selecting foods, in particular chilli and chilli products, avoid those with abnormally red colour or sold at unreasonably low price.
  4. In case you find any foods particularly chilli and chilli products with unnatural or abnormal colour, inform the Food and Environmental Hygiene Department (hotline 2868 0000) for investigation and other follow-up actions.
  5. Maintain a balanced diet to avoid excessive exposure to contaminants or additives from a small range of food items.

Risk Assessment Section
Centre for Food Safety
August 2006