According to the Vatican, to be a valid Communion host sufficient gluten must be present to bring about confection of the bread. Other substances such as gums or pectin are not permitted and the processing must not alter the nature of the bread.
A German company Franz Hoch, is producing hosts using only Codex Alimentarius quality wheat starch and water (< 20 ppm). This is possible because unlike ordinary bread the hosts are extremely thin. These hosts have official Church approval. Importantly for Coeliacs, they have been approved by the scientific committee of the Italian Coeliac Society and also by the Coeliac Society of Ireland.
These hosts are deemed gluten-free for the purposes of differentiating them by the Coeliac Society from ordinary hosts. But for the purposes of clarity with the Church they are known also as low-gluten hosts. It may be less contentious to describe them to your Parish Priest as ‘low gluten hosts’.
The Church requires Coeliacs intending to use them to obtain a letter from their GP stating that these hosts will not cause problems to the Coeliac person's health and this letter must be submitted to the Bishop for approval. On receipt of approval the patient can commence receiving the host as communion knowing both health and Church are satisfied. The shelf life of the hosts is up to 12 months if stored in a sealed package between 12˚C and 20˚C. Suppliers of communion hosts are listed in the Food List.
Another option is to take the wine, but you must ensure that a separate chalice is used, to avoid cross-contamination, and that the ordinary host is not dipped or has a piece broken off into the wine.
It may be useful to talk to your parish priest if you are diagnosed and discuss what option might lead to least difficulty and awkwardness for you.
For parents of first communion children, it is definitely advisable to use the term low gluten host when discussing the use of the gluten-free host with the priest. This is preferable to a lot of parents rather than using the wine. Also bear in mind that the experience of the child at communion and how delicately the situation is handled, will have a bearing on how dedicated to taking communion they are throughout life. A little forward preparation and ensuring that the priest and any Ministers of the Eucharist are aware and involved can make a big difference to your child’s experience.