Sulphites (220-228) are used in a wide range of foods including dried fruit, fruit drinks, sausages (not in meat in the USA) and potato products such as hot chips and dried potato. We did the sulphite challenge with Deb mashed potato. My son was stuttering slightly before the challenge but by day 3 of eating ½ cup of Deb mashed potato per day, his stuttering was so bad that he would not talk at all. His stuttering continued for 4 months after the challenge stopped. Two years later he has had no sulphites and no speech difficulties.