Acute idiopathic urticaria and exposure to vitamin D

Question:

9/2/2020
I evaluated a 65 year-old female with a history of osteoporosis. She states in February 2020 she began an OTC Vit D3 gel cap 2000 units per cap: took one tab per day. After about one week she developed slurred speech and eye droop and was diagnosed with Bells Palsy. At the same time of this diagnosis she developed hives from head to toe. She was on no other medications but Vit D as stated above. She presents for evaluation of allergy to the Vit D3 gel cap.

PMH: migraine HA, not an atopic female. hx of intolerances to clindamycin, Levaquin (not allergic sounding in nature) but had possible hives after tetanus vaccine as a child. The OTC Vit D3 gel cap has Vit D, soybean oil, corn oil and gelatin. Her endocrinologist gave her a prescription for Vit D2 1.25 mg (50,000) units. Exam: WNL.

My question is about likelihood of VIT D allergy. I believe there is a better chance she had urticaria in relationship to a viral infection that caused Bells Palsy rather than than to the Vit D gel cap. However, the patient is being evaluated for allergy to gelatin (immunocap and I will skin test her) as well as soy, corn-but she eats soy and corn regularly. She does not eat gelatin. Hx of reaction to tetanus as a child to be noted. Do you agree with this approach? I believe most likely we will not find positive skin test to the gelatin or soy or corn. Therefore, if patient needs Vit D are there any challenge suggestions? They come in a capsule to would be difficult to measure.