This is kind of a tough question to answer Dennis. There is someone somewhere that will be allergic to anything you can come up with. Some commonly allergenic woods are the rosewoods (Dalbergia), Lacewood ( a type of Oak from Australia I believe) and various other "exotics". I would also stay away from any of the "Cedars", more for the potential of transfering a taste or smell to the salt or pepper, but also for the allergy possibility. Most of my mills are made from domestic North American hardwoods like Cherry, Maple, Ash, Oak, Beech, Birch. I have also used Black Walnut with no known problems (it is a common allergen). I also coat the inside of my mills with shellac just as an extra measure of protection. There are lists of toxic woods on the Internet if you search if you want to learn more. I have seen mills made from all kinds of woods, laminations of several different woods and so on. I think that most are probably safe as long as you are not actually ingesting particles of the wood itself or breathing in the dust or getting fine dust on your skin-all of which are fairly unlikely with a finished mill. Most of us share your concern for the safety of those who receive our products.