For patients who suffer from fall allergies, ragweed season has traditionally followed a predictable schedule. Symptoms typically begin in late summer, peak around September, and ease after the first frost. But that timeline is becoming less reliable.

Edwin Kim, MD, division chief of pediatric allergy at the University of North Carolina School of Medicine in Chapel Hill, said he is now seeing ragweed allergy weeks earlier than the traditional September start.

"Classically, we've told folks, 'Oh yeah, September, back to school, that's when ragweed will hit,'" he said. "But routinely now we're seeing mid-August." 

Besides a busier clinic, Kim sees another sign that fall allergy season has arrived early. "You can actually tell when you go to the pharmacy and you see all the eye drops are missing from the shelves," he said. 

That shift makes it harder for many clinicians to rely on the calendar alone for telling patients when they should begin treatment.

Start Treatment Before Symptoms Peak

For patients with a predictable history of seasonal allergies, waiting until symptoms are severe can make them harder to control.

"By the time they make it to our clinic, they're pretty miserable," Kim said. Trying to use all the medications in the arsenal at that stage means it may be multiple weeks before the patient starts to get relief, he said.

He recommends establishing a plan before symptoms begin. Get those medicines on board early in the season or even before the season, Kim said; then patients may be able to control the inflammation before symptoms become severe.

The challenge is knowing exactly when to start. Weather can affect when pollen is released and how long it remains in the air, said Leonard Bielory, MD, an allergist at the Airway Health Center in Springfield, New Jersey.

"Due to the extensive rainfall in our region, the ragweed release has been delayed, but it is expected to be one of the highest seasons over the past decade," he said.

Pollen forecasts may help clinicians and patients adjust the timing of treatment. Bielory and his colleagues developed a 3-day pollen forecast with an accuracy exceeding 95%.

"The utility rests on a documented dose-response relationship between airborne pollen and symptoms," he said.

Ragweed Not the Only Trigger 

The traditional distinction between spring and fall allergies can also be misleading in regions where pollen seasons overlap, Bielory said.

In the northern New Jersey and New York City metropolitan area, grass pollen has a second peak in September after an earlier peak in June. That resurgence coincides with ragweed season, he said.

"Northeastern patients are experiencing simultaneous grass and ragweed exposure that is increasing in intensity," Bielory said.

Maaz Jalil, DO, an allergist and immunologist at ENT & Allergy Associates in Morristown, New Jersey, said clinicians should review recent local pollen counts when a patient's symptoms begin earlier or last longer than usual.

"If new allergy symptoms or timing of symptoms is occurring, I would consider allergy testing, even if it has been done previously," Jalil said. 

Testing can be especially useful for people who appear to be reacting to multiple triggers, such as ragweed, grass, mold, or indoor allergens and may benefit from immunotherapy, Jalil said.

Don't Overlook Outdoor Mold 

Outdoor mold spores such as Alternaria and Cladosporium can also contribute to respiratory symptoms later in the season.

Unlike ragweed pollen, which generally drops sharply after frost, some outdoor fungal spores can remain elevated later into the fall.

"Mold-associated symptoms may be particularly noticeable around damp vegetation, leaf piles, compost, wooded areas, gardening, mowing, leaf blowing, or raking, especially when these activities aerosolize spores," Bielory said. 

However, symptoms alone usually cannot distinguish mold exposure from pollen allergy. Instead, clinicians should consider the timing and circumstances of symptoms, along with local pollen and mold data.

One useful question to ask patients is what happens when they do yard work, Bielory said. "A patient who develops marked nasal symptoms, cough, chest tightness, or wheezing during or shortly after yard work deserves consideration of outdoor mold exposure," said Bielory. 

Outdoor mold exposure can irritate the lower airways, especially in patients with poorly controlled or severe asthma.

For patients who develop symptoms around leaves, Bielory recommends avoiding raking, leaf blowing, mowing over accumulated leaves, or handling large piles of damp vegetation when possible. If yard work cannot be avoided, a well-fitting N95 or similar respirator can reduce inhalation of airborne particles.

Other Causes of Persistent Symptoms 

A longer or more intense allergy season can make it tempting to attribute persistent congestion, drainage, or cough to pollen. But clinicians should also consider other causes when symptoms don't follow the patient's usual pattern or fail to respond to treatment, Jalil said.

"Uncontrolled allergies can cause chronic rhinosinusitis or recurrent sinus infections especially if there are structural comorbidities such as deviated nasal septum or nasal polyps, so a detailed physical exam is important," Jalil said. 

Distinguishing allergies from viral infections can be especially challenging in children because symptoms overlap and the timing of fall allergy season coincides with the return to school.

"Allergies will not cause fever," said Kim. "So if you've got an adult or kid that's got fever along with those symptoms, that's a pretty clear sign that this is more infectious than anything else."

Newer-generation antihistamines generally work when symptoms are driven by histamine, so a patient who is repeatedly increasing antihistamines without relief may need to be reassessed, Kim said. 

Know When to Investigate Further

For patients with mild or newly recognized symptoms, Kim recommends starting with standard over-the-counter antihistamines and nasal sprays. But symptoms that persist despite appropriate treatment are a reason to reassess.

"When you get to the case where you're doing all the right stuff, you've started the medicines, you're doing it during the season, and it's not helping," he said, "those would definitely be reasons to come in and, number one, get the testing to help confirm that yeah, it is coming from allergies."

Testing can also help identify patients who may benefit from longer-term treatment. Allergen immunotherapy, including allergy shots, can reduce sensitivity to the allergens driving symptoms. For some patients with ragweed allergy, sublingual immunotherapy is another option.

"The reason that we really promote this immunotherapy is the idea that hopefully we're trying to make the allergy go away — not just treat it for that season, but give you the long-term benefit," said Kim.

Kim, Bielory, and Jalil reported no relevant disclosures.

Lara Salahi is a health journalist based in Boston.