Revenue Ruling 55-261

Revenue Ruling 55-261 is the 1955 IRS ruling that established the special-diet rule for medical expenses on Schedule A. It pre-dates the modern naming of celiac disease, but it is the foundational interpretation that every later celiac analysis builds on.

The ruling's plain-language move is to say that when a special diet is the medically prescribed treatment for a medical condition, the extra cost of the diet over what an ordinary diet would have cost counts as a medical expense. Not the full cost of the special diet, just the increment over what the household would have spent without the medical instruction.

For celiac that mapping is straightforward. The gluten-free version of a food costs more than the non-gluten-free counterpart. The increment is the GF premium. The full price of a specialty item with no non-gluten-free counterpart (xanthan gum, sorghum flour, certified GF oats) counts as a medical expense, not just a premium, because there is no ordinary-cost baseline to subtract; see GF-Only item.

Revenue Ruling 55-261 itself runs only a few paragraphs. CPAs and tax professionals usually cite it alongside Publication 502 and IRS Information Letter 2011-0035. The three together are the chain that supports the gluten-free premium on the medical line.

The ruling is binding interpretation, not a position the IRS has reconsidered. It is not new, and it is not controversial in tax-professional circles. The professional-judgment piece is in the application: what counts as a comparable basket, how to handle restaurants, what level of documentation reads as enough.

For the full walkthrough, read What Publication 502 actually says about celiac.