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Advances in the management of and general understanding about seasonal allergies have continued to accumulate within the past 2 years. Here's a brief rundown.

Oral Phenylephrine Deemed Ineffective

Following a long-standing review, FDA advisors deemed oral phenylephrine ineffective for nasal congestion.

During a meeting of the FDA's Nonprescription Drugs Advisory Committee in September 2023, panelists reviewed the data showing that the common over-the-counter (OTC) decongestant failed to reduce nasal congestion scores in allergen challenge chamber studies or in adults with seasonal allergic rhinitis.

Phenylephrine is an active ingredient in popular cough and cold products including Sudafed PE and Suphedrine PE. A cross-sectional study revealed that from 2012 to 2021, prior to the FDA advisory committee meeting, 19.8 billion units of products with phenylephrine were purchased in the U.S. -- a whopping $3.4 billion in pharmacy expenditures.

However, concerns about removing the only oral OTC decongestant products on the market have kept them on shelves.

Additionally, the findings of inefficacy do not apply to nasal spray products containing phenylephrine.

The FDA began investigating oral phenylephrine in 2007 in response to a citizen's petition. The agency had previously held an advisory committee meeting on this issue, which came out similarly negative.

Most Childhood Allergic Rhinitis Persists to Adulthood

The natural course of pollen-induced allergic rhinitis sees the majority of affected children having the condition persist to young adulthood, a study found.

Nearly three-quarters of patients who were confirmed to have pollen-induced allergic rhinitis at age 4 or 8 years at up to age 24 years. Furthermore, 30% of the affected children eventually developed asthma.

However, over one in five children showed remission from this allergic rhinitis between the ages of 16 and 24, though many remained sensitized. During this time, pollen-specific IgE-levels stopped rising and the average estimated incidence of pollen-induced allergic rhinitis fell from 1.5% to 0.8% annually.

"Thus, it is tempting to speculate that continuous exposure with time, to (high levels of) allergen (cumulated exposure) may result in natural tolerance. It has been proposed that tolerance should be viewed as a dynamic lifelong process and a continuous exposure is needed to maintain or induce tolerance," study authors wrote in the journal Allergy.

"It may be that around 20 years of age is a time-period where this change is starting, supporting the theory that childhood up to adolescence is the most dynamic period of disease progression whereafter natural tolerance becomes more common," they noted.

Immunotherapy for Pediatric Allergic Rhinitis

The available evidence favored over subcutaneous immunotherapy for safety in the management of pediatric allergic rhinitis, according to a systematic review and meta-analysis of 50 studies.

Indirect and direct comparisons between the two immunotherapy methods suggested they were associated with similar symptom scores, medication scores, new sensitizations, and development of asthma.

However, there was a significantly lower rate of treatment-related adverse events observed among patients who received sublingual immunotherapy (pooled RR 0.17, 95% credible interval 0.11-0.26).

"[Subcutaneous immunotherapy] can cause serious adverse events and even anaphylactic shock, while [sublingual immunotherapy] can be safely self-administered, and local adverse reactions (primarily limited to oral discomfort) caused by [sublingual immunotherapy] are often mild and subside without treatment," the authors noted in Frontiers in Immunology.

Climate Change and the Future of Allergies

Last September, the European Respiratory Society (ERS) released a position statement that warned of the risks of climate change for those with respiratory conditions. Longer allergy seasons, as well as the introduction of new allergens, are expected to affect people around the world. The timing and physical areas impacted during allergy seasons are likely to shift, and increases in thunderstorms, alongside other cases of extreme weather, may impact outbreaks of allergic asthma.

The ERS statement advocated for stricter air quality standards -- namely changes to the World Health Organization's (WHO) 2021 Air Quality Guidelines -- citing a 2019 estimate that attributed 6.7 million deaths worldwide to small particulate matter.

The position statement came on the heels of notable 2023 summer wildfires impacting the U.S., which was linked to an uptick in asthma-related visits to the emergency department. New York City reported a nearly 82% increase in visits, while nationwide, visits were 17% higher than expected. Exposure to wildfire smoke and extreme heat has been linked to worse respiratory and cardiovascular health -- both of which, experts warn, are exacerbated by climate change and disproportionately affect Latino, Black, Asian, and other racially marginalized residents, as well as low-income communities.

Seasonal Allergies Now Affect One in Four Adults

The prevalence of seasonal allergies reached 26% of U.S. adults and 19% of children in recent reports from the National Center for Health Statistics.

Based on data from 2021, the prevalence of pediatric seasonal allergies rose since 2011, when an estimated 17% of children reportedly had respiratory allergies.

In the new data, seasonal allergies were most prevalent in adolescents ages 12-17 years (24%), followed by children ages 6-11 years (21%), and then children 5 years and younger (10%).

Among adults, seasonal allergies were most prevalent in those ages 45-64 years (28%), followed by those ages 65-74 (26%), ages 18-44 (25%), and 75 and above (22%). People over the age of 75 experienced the lowest rates of all allergic conditions.

Adult women were more likely to experience seasonal allergies (30% compared with 21% of adult men). Seasonal allergies were slightly more common among boys (20% compared to 18% of girls), and were most prevalent in non-Hispanic Black children at 21%.

Study authors cautioned that the COVID-19 pandemic had interrupted interviews for the study. Just over 60% of adult participant interviews were conducted at least partially by phone.

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