I have a patient who states that she has a glycerin allergy. She cannot give me specific details, as she states the reaction she had to glycerin is remote (greater than 20 years ago) but thinks she may have headaches related to glycerin, and may have had some throat symptoms, that she states were not life threatening. She is also concerned about future vaccinations, but from the vaccines practice parameter, it appears that only BCG and the Vaccinia vaccine contain glycerin, as far as I can tell. Is this correct? She presents to the office to get testing for glycerin, and for glycerin desensitization. I have done some research but cannot find any resources for glycerin testing or desensitization. Do you have any experience with testing for glycerin or desensitizing someone to glycerin? Thanks for any assistance or insight you can give.
I am not aware and could not find any reports in the medical literature of glycerin allergy. It is not biologically plausible since glycerin is a component of all cellular membranes, glycerin is used in numerous allergenic extracts both for testing and treatment (3) and glycerin is not of sufficient molecular size to evoke an immune reaction. There are glycerin diluents, usually containing 10% glycerin, available from allergenic extract manufacturers and prick testing could be performed with this control to reassure your patient of the absence of any reactivity. However, glycerin may cause an irritant reaction when used for skin testing (1,2). Therefore, the results might increase your patient’s anxiety.
In summary, I am skeptical that your patient has a glycerin allergy or immunologic sensitivity and would reassure her that there is no evidence of significant reactions to glycerin. You could perform skin testing with a glycerinated diluent to confirm your statement, but glycerin may cause an irritant reaction and add to the patient’s concern. I would reassure the patient and if they do not accept then challenge with a prick test followed by a subcutaneous injection of 0.5 ml of a 10% glycerinated diluent.
1. Effects of diluents on skin tests.
JL Menardo, J Bousquet, A Bataille, G Restagny… - … of allergy, 1983 - europepmc.org
The role of diluents and preservatives on skin tests was examined in 41 allergic patients.
The effect of glycerol in intradermal tests was studied. Concentrations of five percent glycerol
were shown to induce a significant wheal which was not inhibited by clemastine fumarate,
suggesting a direct toxic effect without the participation of histamine release. Twenty five
Dermatophagoides pteronyssinus allergic patients were prick tested with standardized and
lyophilized extracts reconstituted either in saline, 50% glycerol or human serum albumin …
2. Guerin, B., and S. Tioulong. "Analysis of the non‐immunological activity of allergen extracts in cutaneous tests." Clinical & Experimental Allergy 9.3 (1979): 283-291.
3. 3/30/2015: Glycerinated extracts for allergy testing
I am struggling to find the right answer that why clinician use glycerinated food allergen extract while performing Skin prick test. According to my understanding, glycerol can cause irritation (not allergy) itself to some people, then what is the possible reason to use it. Do you have any idea about it?
I agree there appears to be a paradox in the use of glycerin as it does have irritating properties. The explanation is that glycerin has desirable properties. The major desirable property is that glycerin stabilizes the allergen proteins and prolongs the shelf life of the testing reagent. Also 20% glycerin provides a bacteriostatic effect reducing likelihood of bacterial contamination of the testing reagent. Glycerin content of greater than 50% is prone to causing significant discomfort if injected as an immunotherapy vaccine (allergy shot). Large local reactions (swelling and redness) from an allergy injection does not correlate with glycerin content, indicating that the glycerin does not cause a reaction that is likely to be confused with a positive skin test.
Fresh food tests are also used to assess sensitivity to allergens that are more labile. These do not require a stabilizer and are generally performed by touching the test implement to the fresh food and then to the skin of the test subject.
In summary, the concentration of glycerin used in allergy test reagents is not sufficient to cause a false positive reaction and serves to increase the shelf life and reduce bacterial growth in the product.
I hope this information is of help.
All my best.
Dennis K. Ledford, MD, FAAAAI