How is wheat starch made? Why is some starch said to be more toxic than others?

Very few celiacs are likely to have any reaction to topical gluten contact. In order for a gut reaction to occur, it is likely that direct contact with the gut lumen is required. Many people with celiac disease have everyday contact with gluten (for instance, bakers with celiac disease who have contact everyday with wheat flour), and do not have any reaction to it. However, there are, on rare occasion, people who have had an anaphylactoid response to gluten, and these people should avoid gluten in all forms. Also, topical gluten breathed into the upper airways may cause symptoms of allergic rhetinitis in rare instances. If there is a simple alternative to a shampoo, cosmetic, etc., you may want to use the non gluten containing product.
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The incidence of celiac disease in the general population can vary from country to country, but could be as high as 1 in 150. For more information regarding statistical research on celiac disease, see the Open Original Shared Link page.

The average gluten-containing diet contains roughly 10-40 grams of gluten per day. This figure is based on the amounts of gluten in your average slice of whole wheat bread, which contains around 4.8 grams of gluten (10% gluten by weight), and the amount of gluten in a serving of pasta, which is roughly 6.4 grams of gluten (11% gluten by weight). The smallest amount of gluten which has been shown by a biopsy to cause damage to a celiac is 0.1 gram per day (Catassi et al.). This is approximately the amount of gluten contained in 1/48th of a slice of bread! The biopsies in this study showed an increase in intraepithelial lymphocyte count, one of the earliest signs of damage. The challenge was on 10 patients (children) for 28 days each. Four of the patients showed an increase in IgA...