The package insert of fluoride products states that asthma is a contraindication with less than 1 case per 10,000 applications. There are references in the literature that this contraindication applies only to asthmatics with history of hospitalization or severe asthma but that is not the wording in the package insert. I could not find the exact reason for the contraindication although some reviews mention “possible allergy” to either the fluoride or the colophony that is used for adherence to the tooth (a derivative of pine resin and potential cause of contact sensitivity and inhalation can cause asthma). Although fluoride is an element and is of insufficient size to be recognized by the immune system, it is possible that the reactive halogen could attach to proteins to form a hapten recognized by the immune system. I raise this possibility as there are multiple reports of fluoride, including double blind challenges, causing urticaria, exfoliative dermatitis, atopic dermatitis, stomatitis, gastrointestinal and respiratory allergy (Shea). I am not aware of double-blind challenges inducing asthma and I am not aware of specific antibody being described to fluoride but positive patch testing (cell mediated immunity) has been described.
In summary, there is some evidence in the literature of a specific reactions to fluoride products although the specific immune mechanism is not defined. Asthma is listed as a contraindication to the use of at least one fluoride varnish. Therefore, I would conclude that fluoride varnish should not be used, or used only with a high level of caution, in patients with asthma. I would assume that the risk is much greater with uncontrolled asthma but this is not clear.
I have enclosed an archived question from Ask The Expert that mentions the asthma contraindication but does not provide any additional explanation for the mechanism.
Noble, James. "Fluoride varnish for the teeth." Vital 5.1 (2008): 39-39.
Use of oral fluoride varnish in children with allergy to foods
Is it safe to apply Fluoride varnish containing colophony to a child with an epipen for severe allergy to say e.g. nuts in a nursery/school setting?
A: I know you are familiar with the information that I have copied below regarding the contents of oral fluoride varnish, and its contraindications. However, I have added this information to my answer for the benefit of our readers, who are mostly physicians and who would not be expected to be familiar with the contents of the varnish and its contraindications.
I can see no reason, based on the contents of the fluoride varnish, why a child with food allergy, who does not have asthma, would be at any increased risk for an adverse response to oral fluoride varnish.
So, in my opinion, it would be safe to administer fluoride varnish to food-allergic children as long as there is no history of asthma.
Thank you again for your inquiry and we hope this response is helpful to you.
6.1 List of Excipients
White Wax (E901)
Raspberry Essence (containing Ethyl Butyrate, Geraniol, Iris Resinoid, Isoamyl Acetate, Jasmine Absolute, Vanillin and Propylene Glycol).
Hypersensitivity to colophony and/or any other constituents.
Phil Lieberman, M.D.
I hope this information is of help to you and your patient.
All my best.
Dennis K. Ledford, MD, FAAAAI