Vitamin D and allergic rhinitis: A mini-review

Table 1 Immune response in normal vs allergic rhinitis individuals

Features	Normal immunity	Allergic rhinitis
Th cell balance	Balanced Th1/Th2	Th2 skewed dominance
IgE production	Low IgE levels	High IgE levels promoting hypersensitivity
Epithelial barrier	Strong, intact	Impaired, leaky barrier facilitates allergen entry
Inflammation	Controlled, self-limited	Chronic, persistent nasal inflammation
Mast cell activation	Minimal under normal conditions	Heightened activation and mediator release
Clinical outcome	No allergic symptoms	Sneezing, itching, rhinorrhea, congestion

IgE: Immunoglobulin E; Th: T-helper.

Table 2 Vitamin D and allergic rhinitis

Classification
AR	An immunoglobulin E-mediated inflammatory condition
	Triggered by exposure to airborne allergens
Vitamin D	A hormone with immunomodulatory properties
	Deficiency in vitamin D has been implicated in the pathogenesis of AR
Immunological mechanisms	Modulates both innate and adaptive immune responses
	Suppresses the production of pro-inflammatory cytokines
	Enhances the development and function of regulatory T cells
Clinical evidence	Studies on vitamin D supplementation have yielded mixed results
	Some evidence suggests potential improvement in AR symptoms

AR: Allergic rhinitis.

Table 3 Standard protocols in clinical randomized controlled trials on vitamin D supplementation for allergic rhinitis

Protocol component	Details
Patient selection	Clinical diagnosis of allergic rhinitis. Confirmed vitamin D deficiency (< 20 ng/mL). Exclusion: Chronic systemic illness, immunodeficiency, high-dose steroids
Supplementation regimen	Vitamin D3 (cholecalciferol): 1000–2000 IU/day. Oral route preferred. Duration: 8-12 weeks
Concomitant treatments	Standard antihistamines (e.g., cetirizine, loratadine). Some trials include intranasal corticosteroids. Medications maintained at stable doses
Outcome measures	Symptom scores (e.g., total nasal symptom scores, visual analog scale) at baseline and end of study. Serum 25-hydroxyvitamin D levels pre-intervention and post-intervention
Immunological assessments	(In select trials) CD4+CD25+Foxp3+, Treg levels, cytokine profiling (e.g., IL-4, IL-10, interferon-γ)
Monitoring and follow-up	Follow-ups every 4 weeks. Supplement compliance via pill count/self-report. Monitoring for side effects/toxicity

IL: Interleukin.