Table 3:

Quantity/Concentrations of Excipients Used in the Literature and by Authors for Allergy Testing

Excipient	Notes on Testing	SPT	Intradermal	Blood testing modalities	Oral Challenge in Skin Test Negative Patients
Polyethylene derived compounds
Polyethylene glycols of various molecular weights (300–20,000)	Testing strategies to assess the possibility of PEG allergy (Figure 3) are under active study, with authors recently reporting the utility of using PEGs of the highest molecular weight possible as a key feature for improving clinical sensitivity when SPT to lower MW are negative.21 Cross reactivity to polysorbate 80 and poloxamers, which share long chains of repeating ethylenes can possibly be determined by skin testing. Translation of skin test cross-reactivity into clinical cross-reactivity upon drug challenge remains to be determined. Titrated SPT must be performed stepwise and with caution, as systemic reactions can be induced. When PEG allergy is suspected, the patient should ideally be skin prick tested with the suspected culprit product, low MW PEGs (PEG 300, PEG 2000) and with higher MW(PEG 3000 and PEG 6000), and the PEG derivatives poloxamer 407 and polysorbate 80 due to possible cross-sensitization. If SPT is positive, the diagnosis is confirmed.  If SPT with low MW PEGs is negative but clinical suspicion is strong, SPT with high MW PEGs (PEG 20,000 0.1–200mg/ml in stepwise, increasing concentrations) is recommended. If SPT is positive, the diagnosis is confirmed (Figure 3). Once SPT is positive, further testing with higher MW PEGs is not necessary as this may induce systemic reactions due to the increasing allergenicity in increasing MW PEGs. If SPT is continuously negative, IDT or graded challenges can be considered.21 The use of intradermal corticosteroid preparations containing PEG 3350 and polysorbate 80 has been reported in some cases,15 but may come with a risk of irritant responses when the steroids are used in the range of 1–10mg/ml.	See Bruusgaard et al. as primary reference.21  Initial test with PEG 300 (1000mg/ml), 2000 (500mg/ml), 3000 (500mg/ml) and 6000 (500mg/ml) increasing to PEG 20.000 in tenfold step increases from0.1 up to 200mg/ml. Testing is stopped on reaching a positive test Gentofte Allergy Clinic, Denmark (unpublished data) > 600 negative controls on PEG 300, 3000 and 6000, > 200 negative controls on PEG 2000 and > 30 negative controls on PEG 20,000 in above concentrations	Not routinely performed, sterile grade reagents not available. Anaphylaxis has been reported.	Under research15,18,22
Polyethylene glycol 3350 (using commercially available OTC products)		1.7–170mg/ml when starting from 17gm packet mixed with 100cc sterile water	Not routinely performed, unless sterile grade reagents are available. Anaphylaxis has been reported.		Challenges using Gaviscon (alginic acid) double action tablets (20,000)9 Open titrated challenges using PEG 335013 850 mg oral challenge, using 5ml of 170mg/ml concentration has been used by authors (Krantz, Stone) after 1st dose mRNA vaccine anaphylaxis, prior to 2nd dose vaccine attempt.84 Note: common side effect of sticky mouth sensation.
Methylprednisolone acetate (PEG 3350 containing)		0.4mg/ml, 4mg/ml	0.4mg/ml, 4mg/ml of methylprednisolone acetate can be used15 but not enough evidence on irritant doses.
Poloxamer 407		100mg/ml21 Gentofte Allergy Clinic, Denmark > 600 negative controls	Not routinely performed, sterile grade reagents not available
Poloxamer 188		100mg/ml Gentofte Allergy Clinic, Denmark > 10 negative controls	Not routinely performed, sterile grade reagents not available
Polysorbate 80		200mg/ml21 Gentofte Allergy Clinic, Denmark > 600 negative controls	Not routinely performed, sterile grade reagents not available
Triamcinolone acetonide (contains polysorbate 80)		0.1mg/ml, 1mg/ml	0.1mg/ml, 1mg/ml of triamcinolone acetonide can be used15 but not enough evidence on irritant doses.
Non-polyethylene derived compounds
Carboxymethylcellulose	Skin testing concentrations have not been validated, but skin prick testing can be performed using CMC powder dissolved in saline.  Certain medications, such as eye drops containing CMC as the only ingredient, along with injectable corticosteroids containing CMC, have been useful in the authors’ experience (Figure 4). Specific IgE testing has been used in a research capacity and appears to have potential utility.36	Skin prick tests using technique with CMC powder dissolved in saline Skin prick tests with undiluted CMC single ingredient eye drops Gentofte Allergy Clinic, Denmark  > 600 negative controls with eyedrops 10mg/ml	No published protocols. Use sterile products containing CMC.  (Figure 5 shows testing using sterile CMC eye drops) 3 healthy controls, not enough information on irritant doses.	Under research36	Oral challenges have been performed using 10mg, 30mg oral doses.37
Triamcinolone acetonide (contains carboxymethylcellulose)		0.1mg/ml, 1mg/ml	0.1mg/ml, 1mg/ml of triamcinolone acetonide can be used15 but not enough evidence on irritant doses.
Mannitol	Skin testing has been positive in a few of the published cases with a clear history suggestive of allergy to mannitol. Tests performed using a 1:10 (20mg/ml) or 1:100 (2mg/ml) dilution of 200mg/ml mannitol for intradermal testing. The severity of clinical reactions, skin test positivity and tryptase increase in one case42 suggests an IgE mediated mechanism and this has been confirmed by the demonstration of mannitol specific IgE in one report.41	2mg/ml, 20mg/ml85  Gentofte Allergy Clinic, Denmark  > 400 negative controls on 150mg/ml	2mg/ml, 20mg/ml39,85	Under research41	Oral challenges eliciting symptoms have been performed using oral mannitol laxative39
Povidone	Testing can be performed by skin prick testing (SPT) which has been employed safely in several reports. In the authors’ experience, a commercially available eyedrop containing 50 mg/ml povidone has tested positive in one case and negative in 475 controls.  Intradermal testing and specific IgE against povidone havebeen used.47,48	50mg/ml skin prick test has been used44 Gentofte Allergy Clinic, Denmark > 400 negative controls	50mg/ml povidone iodine (aqueous solution) diluted 1:100 with normal saline (0.5 mg/ml) has been used, 1 negative control.48	Under research47
Protamine	Skin prick testing to protamine can be performed at concentrations that are similar to NPH insulin (300–350 μg/ml) diluted from stock protamine 10mg/ml, with intradermal testing in a range of 0.3 to 30 μg/ml.49 Protamine appears non-irritant at 10mg/ml for skin prick testing and up to 0.01mg/ml for intradermal testing.51 It is important to note that skin sensitization without signs of overt allergy to insulin injections may occur in diabetics, although it is not known whether this poses a risk of anaphylaxis when high dose IV protamine is administered during cardiac surgery. Antibody testing to detect serum specific IgG and IgE has also been reported and is commercially available.56 Testing strategies that consider the possibility of reactivity to insulin itself along with other insulin ingredients such as metacresol are recommended.	10mg /ml	0.01 mg/ml. Potentially irritant at higher  concentrations.	Under research56 Commercially available
Gelatin	Skin prick testing using commercially available food-grade gelatin diluted with saline to a concentration of 1g/ml as per current allergy practice parameters (Figure 5). Bovine and porcine specific IgE testing can be helpful confirmatory tests.  Patients can sometimes demonstrate specific IgE sensitization to one form of mammalian gelatin but not the other,66,67 but in practice they should be considered cross-reactive due to lack of information on whether this has clinical significance and labeling that does not report gelatin source.	1 g/ml using food grade gelatin has been used.	Not typically done since sterile grade reagent is preferable.	Specific IgE testing is com-mercially available, Positivity sometimes varies by gelatin (bovine, porcine)	Oral challenge can be performed in those with unlikely allergy.
Galactose-alpha-1,3- galactose	The diagnosis of alpha-gal allergy primarily relies upon the presence of serum specific IgE directed against alpha-gal in patients with a characteristic reaction history. When trying to determine whether alpha-gal is the culprit behind an individual patient’s reaction to a drug, academic centers in endemic areas have utilized strategies including skin testing, drug-alpha gal sIgE binding assays, basophil activation, and drug and food challenges.	Beef, pork, lamb skin prick tests using standardized reagents at 1:20 wt/vol have been used86	Intradermal tests sometimes used in research setting86	Mainstay of diagnostic testing is positive serum specific IgE in a patient with likely history.87,88	Oral challenges using sausage patties have been performed to elicit or rule out symptoms.89 Pork kidneys have very high content, used in some centers.90