Allergies may be worse thanks to climate change
If you’ve been sneezing, sniffling, coughing or feeling fatigued from allergies lately, you’re not alone.
The Bay Area is in the midst of what has traditionally been considered peak allergy season, March and April. But climate change is leading to higher pollen counts earlier in the year and prolonging those periods of high pollen, according to allergists and recent research — offering one potential explanation for why seasonal allergy sufferers may feel crummier than usual.
“Even though the rain hasn’t quite stopped yet, we’ve already seen an increase in tree pollen starting in the last week or two of March,” said Dr. Jyothi Tirumalasetty, a clinical assistant professor of allergy and immunology at Stanford. “We’re seeing things start earlier and earlier, and being a little more intense than what we’ve seen in the past. The wetter, warmer weather patterns we’ve seen this year and last year is probably the reason for that.”
The “growing season” — the amount of time plants have to grow and release allergen-inducing pollen — is on average 19 days longer than it was in 1970, according to an analysis of nearly 164 U.S. cities released in March by Climate Central, a nonprofit that researches climate change.
That means a longer pollen season and, potentially, 19 more days of allergy symptoms, said Dr. Lisa Patel, a clinical associate professor of pediatrics at Stanford who studies the impact of climate change on health.
The analysis was not able to look at California specifically, likely because the seasons are less pronounced here compared with the East Coast and the South, which have more distinct hot and cold seasons, Patel said.
But its overall findings echo that of previous research, including a 2023 review published in the Annals of Allergy, Asthma and Immunology that analyzed many studies on how global warming worsens allergic disease. The review found that climate change and global warming are increasing pollen concentrations and that pollen season is starting earlier and lasting longer.
The Bay Area received rainfall this past winter that was slightly above average levels. More rainfall generally means more vegetation. The rain suppresses the pollen count, but once the weather gets drier and warmer, weeds, trees and grasses start putting pollen out into the air.
“The rain we’ve had has kept the pollen counts down. Then when it dries out like it is now, it can get really bad really quickly,” said Dr. Michael Mulligan, division chair for allergy immunology at Sutter’s Palo Alto Medical Foundation.
In the Bay Area, most seasonal allergy sufferers are allergic to tree pollen or grass pollen, local allergists say. Tree pollen typically triggers people’s allergies earlier in the year — around March, April and May — because trees pollinate earlier. That’s followed by grass pollen, usually in April, May and June, and then weed pollen in late summer.
The Bay Area has unique regional microclimates and tree populations that can greatly affect people’s allergies. In San Francisco, for instance, people tend to have more cedar tree allergies because there are more cedar trees in the city, while the South Bay has more olive and oak trees and the East Bay has more grass, said Dr. Andrew Hope, an allergy specialist at Kaiser Permanente.
Wind and proximity to the ocean are also factors. The East Bay and Central Valley have more accumulation of pollen because winds travel over more areas with plants and trees.
“Patients who live in San Francisco tend to have less trouble because they have the ocean breeze blowing pollen away,” said Mulligan, of Sutter. “The further south you go on the Peninsula, the worse the allergies get. If you move from San Francisco to the South Bay, allergies are often worse during the spring, and if you move to Morgan Hill or Gilroy, symptoms are worse still.”
Mulligan said he often sees college students from the Bay Area struggle with seasonal allergies when they go to UC Davis or Chico State for school because the pollen count is much higher in the Central Valley.
The doctors offer the following tips for managing seasonal allergies:
Close your windows at night.
Wear a mask and/or sunglasses if spending a lot of time outdoors.
Change clothes and shower after spending time outdoors. Pollen that’s not visible to the naked eye can stick to eyelashes or clothes. Take off your shoes so you don’t track pollen indoors.
Over-the-counter antihistamines, nasal spray and olopatadine eye drops can help. If you know you have severe allergies every spring, start taking medications a week or two before you think you’ll need them so the medication is in your system.
If over-the-counter medications aren’t enough, consider talking to your doctor about having an allergy test done or getting allergy shots.
Check the pollen count in your area to see if you need to take extra precautions outdoors. The National Allergy Bureau, run by the American Academy of Allergy, Asthma and Immunology, has an online tool that shows pollen and mold count from pollen counting stations across the country, including the Bay Area.