Brown FK (E 154) is a yellowish-brown mixture of six different azo dyes. It may only be used for the coloring of smoked herring, as it is traditionally done in the UK. In animal studies, damage to the heart and liver were noted. Many organs are discolored by a metabolic product of Brown FK. Brown FK can trigger allergies. The EU maximum allowable quantity is in ready-to 20 mg / kg and may not be used for drugs and cosmetics in the EU.