Epidemiologic studies highlight the increasing prevalence of vitamin D deficiency and insufficiency and its association with an increased risk of autoimmune diseases and poor respiratory function, including asthma.

These and additional studies have raised interest in the immunomodulatory properties of vitamin D beyond its well-established role in calcium homeostasis and bone health. Vitamin D has been shown to influence the function of cells intrinsic to innate and adaptive immunity.

This review discusses recent evidence that vitamin D promotes—both directly and indirectly—regulatory or suppressor T-cell populations with the capacity to inhibit inappropriate immune responses that cause disease, suggesting that this property may in part underpin the epidemiologic findings.

Histamine and the histamine receptors are important regulators of a plethora of biological processes, including immediate hypersensitivity reactions and acid secretion in the stomach.

In these roles, antihistamines have found widespread therapeutic applications, while the last receptor to be discovered, the H4 histamine receptor, has become a major target of novel therapeutics. Recent studies involving human genetic variance and the development of mice lacking specific receptors or the ability to generate histamine have shown roles for the histamine pathway that extend well beyond the established roles. These include identification of previously unappreciated mechanisms through which histamine regulates inflammation in allergy, as well as roles in autoimmunity, infection, and pain.

As a result, antihistamines may have wider applications in the future than previously predicted.

Despite the well-known benefits of subcutaneous immunotherapy (SCIT), adverse reactions include both local reactions (LRs) and systemic reactions.

An LR is a well-known adverse event associated with SCIT injections and is defined as any swelling located at or near the injection site following allergen injection. Concerns that LRs might predict systemic reactions have historically motivated allergists to dose adjust for LRs.

More recent data have dispelled this notion, although many allergists continue to dose adjust for other reasons. This article discusses the historical response to LRs and dose adjustments and reviews the most recent literature addressing LRs to SCIT.

Treatment options, although they are either unproven or not studied, are offered as an alternative to routine dose adjustments for LRs. Education remains the foundation of physician–patient communication concerning LRs.