This guidance considers the needs of those suffering from coeliac disease and those suffering from alcoholism in relation to the Eucharistic celebration.
The elements for Holy Communion in Canon Law and good practice requires that the bread of the eucharist, which may be leavened or unleavened, must be "of the best and purest wheat flour that it is convenient to obtain" (Canon B.17). In the spirit of this where 'ordinary' bread (i.e leavened bread) is used, the supply ought to be of fine quality bread rather than cheap, mass produced bread. Where unleavened bread is used, this can either be the widely used forms of wafer bread (including thicker biscuit-type wafers which can be broken into many pieces) or it can take the form of matzah, i.e. the Jewish unleavened bread used at the Passover Meal which comes in the form of a biscuit.
Gluten-free bread, usually in wafer form and square in shape for easy recognition, is also both legal and pastorally desirable for those suffering from coeliac disease. Canon B.17 is not intended to restrict any of these possibilities, but it does point to the requirement of quality in what is provided. Only the best should be offered to God in the service which is the living memorial of Christ's Passion.
Equally, those for whom any alcohol would be medicinally harmful can be legally and properly provided with non-alcoholic wine. This is wine from which the alcohol has been extracted and is readily available commercially. This is not the same as using unfermented grape juice or other fruit juices, which are not wine and are neither Scriptural nor Canonical. A very small quantity of non-alcholic wine can easily be consecrated for such persons in a clinical chalice (i.e. the small cup sometimes used in home Communions) or in a secondary chalice.
As with gluten-free bread, this should only be used for the particular communicants for whom it is prepared. An alternative way of communicating people with an alcoholic predisposition, where the merest drop would not affect them is by 'intinction' (the consecrated bread being carefully dipped in the consecrated wine, with care taken that fingers do not contaminate the contents of the communion cup). Either method is perfectly proper depending on the circumstances.
Non-gluten wafers are obtainable from Charles Farris and Kevin Mayhew. Non-alcoholic wine is obtainable from Charles Farris, Frank Wright and Mundy and Kevin Mayhew.