There are a number of reasons why homemade items are necessary for SCD™ instead of the "convenient" store-bought items.
The 2% rule: There is a rule that allows some ingredients that constitute less than 2% of the total weight or volume unnecessary to report on the ingredient list. This can include sugar and other illegal ingredients, since these do not fall under the list of usual allergens.
Store-bought products often pass through many sets of hands before they are put in the final package. For example, some juice concentrates can be made in one plant and then shipped to another plant where water is added and then they are bottled. The final producer can "honestly" say they did not add any illegals but what about the first producer of the concentrate. The original concentrate does not even have to be made in the same country as the final bottler.
Commercial producers are not bound to report some of the ingredients listed in their foods. They can use processing aides, enzymes etc., that are used in the production of the food but are not technically an ingredient. When you make foods for your children you know "exactly" what you are putting into it.
Buying foods such as cookies that are not listed on this site as suitable SCD™ products, can lead to trouble. Some producers may unintentionally use illegal ingredients. For example, a commercial producer uses honey that is not pure (i.e., cut with corn syrup) but includes honey on the ingredient list. The end result is that your child is unknowingly ingesting illegals.
Some companies blatantly lie about the ingredients in their products.
Tips to ease the transition from the use of commercial products to homemade foods:
1. Make large batches of items, for freezing or canning.
2. Contact local volunteer services to have someone assist in the
weekly preparation of foods.
3. If finances allow hire a part-time cook/chef.
4. Contact other local SCD'ers for local ingredients that are legal.
From: SCD Listserve