If you have an allergy to alcohol, then the brandy-based remedies should be avoided.  You should also be aware that even the alcohol-free remedies (suspended in vegetable glycerine) have been made from mother tinctures that will have been preserved in alcohol.  We have been asked about nut allergies and whether remedies such as Walnut might trigger a reaction.  The Walnut remedy (as with other nut-producing plants such as Beech and the Chestnuts) is made from the flowers of the tree, not from the nut, but as always, you should seek the advice of your doctor if you have a concern.  You may also wish to contact the manufacturer of the remedy brand you use for further information about any potential traces of material to which you are sensitive.