I don't think believing the Holy Eucharist cannot harm the gluten intolerant is at odds with the accidents remaining. Why could Our Lord not make the gluten-intolerant tolerant of gluten during, and for some time after, the reception of the Eucharist?
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An accident is some quality that an object has that are not its substance. These are things like taste, color, smell, and so on. This would include chemical reactivity, and every other physical property that it has. So, if some substance makes a person sick, that is an accident of that substance.
This can be more easily explained by saying there is no experiment that someone can do to a host to determine if it is consecrated or not, since any experiment would only tell us the accidents of the host, not its substance.
So, if a certain type of host makes a particular person sick, that is an accident of the host.
Let's see what the Council of Trent says:
If anyone says that in the sacred and holy sacrament of the Eucharist there remains the substance of bread and wine together with the body and blood of our Lord Jesus Christ, and denies that wonderful and singular conversion of the whole substance of the bread into the body, and of the entire substance of the wine into the blood, the species [accidents] of the bread and wine only remaining, a change which the Catholic Church most fittingly calls transubstantiation: let him be anathema. Denzinger 884.
So the Council of Trent tells us that the species or accidents of the bread and wine remain after consecration. Therefore the bread and wine will behave exactly the same, on a physical level, both before and after consecration.
If this idea were true, then it would be possible to do an experiment with a sacred host to tell if it is consecrated or not, by giving it to someone with celiac disease, and then based on whether they get sick or not you would know if it is consecrated. This is not only contrary to the Council of Trent, it is contrary to the entire Catholic concept of the Holy Eucharist, which is that Our Lord's presence is a mystery since He is physically undetectable in the sacred host.