Allergic asthma is a disease of chronic inflammation due to a hypersensitive immune reaction to an allergen such as pet dander, pollen, or dust mite excretions. It is characterized by airway hyperresponsiveness (AHR), an increased tendency for airways to constrict, and airway remodeling. The disease is more common in developed countries than developing countries.
Researchers are interested in vitamin D and asthma because of vitamin D’s ability to influence the immune system. It is well-established that vitamin D is an immunomodulator. An immunomodulator is a substance that balances the immune system, with the ability to stimulate a weak immune response and dampen an overactive response.
However, the effect of vitamin D on allergic asthma is under debate. Previous studies have shown no effect of vitamin D supplementation on inflammatory markers in the lungs, while other studies have shown reduced vitamin D levels are associated with impaired lung function and AHR.