Mysterious new allergies? 6 reasons why adult-onset allergies are on the rise.

Every year, more than 50 million adults suffer from allergies. While it’s common to develop allergies as a child, many adults find they develop new allergies as they age.

“Nobody is born with allergies. While they often develop in childhood... they can occur at any point in one’s life, regardless of their age, gender or ethnicity,” Dr. Shyam Joshi, an allergist and assistant professor of medicine at Oregon Health and Science University, tells Yahoo Life.

So why does it happen? Here are six reasons why allergists say you can develop adult-onset allergies, and what to do about it.

1. Climate change

Climate change isn’t just changing the environment, it’s leading to notable changes in environmental allergies, Joshi tells Yahoo Life. “Not only are we seeing higher levels of pollen in the air, but the allergy season is lasting longer ... and warm weather leads to increasing plant growth and pollen production,” he explains. According to the United States Department of Agriculture, new research shows that pollen seasons start 20 days earlier, last longer and manifest more pollen than has been seen in decades, due to climate change. In turn, these exacerbate allergies, according to Dr. Roberto Garcia-Ibá?ez, a board-certified allergist with the AllergiGroup, tells Yahoo Life. These changes are “leading to a rise in new-onset adult allergies,” says Ogden.

2. Hormonal changes and pregnancy

Women who are experiencing hormonal fluctuations might develop allergies later in life. As a result, Garcia-Ibá?ez recommends that women pay close attention to how their cycles correspond with allergy symptoms. However, “the relationship between allergies and hormones is complex and not well understood,” says Joshi. Girls are much more likely than boys to develop environmental allergies after puberty, he says. Other women develop new allergies during menopause. Doctors aren’t sure why women are susceptible to developing new allergies during these key times in their lives. However, Dr. Tania Elliott, an allergist and Chief Medical Officer of Virtual Care at Ascension says it may have to do with fluctuations in estrogen. Pregnancy is another "key period when hormonal shifts can lead to changes in the immune system,” says Dr. Joshi. However, the Asthma and Allergy Network finds that allergies can either worsen, stay the same, or, for some women, even improve during pregnancy.

3. Changes in immune system

As we age, our immune systems change. This can lead to developing new allergies or a worsening of existing allergies, Joshi says. This is because when the immune system shifts, it can overproduce specific inflammatory mediators that cause us to become more sensitive to allergens, he explains. Additionally, some women develop autoimmune issues as they age, Elliott says. “Autoimmune issues are correlated with people developing skin allergies, particularly hives,” she says.

4. Increased exposure to allergens

Sometimes environmental allergies don’t develop until someone is exposed to the allergen multiple times. Sometimes, a person isn’t exposed to an allergen enough times during childhood to show an allergic response, and they suddenly see this change in adulthood. Dr. Gary Soffer, a Yale School of Medicine allergist-immunologist tells Yahoo Life that some allergies appear in adults for the first time “because the allergic part of the immune system needs multiple exposures before it develops a response.”

5. Changes in skin

Contact dermatitis, a kind of skin allergy that causes dry, itchy skin or a rash, often gets worse in adulthood. Joshi explains that this probably occurs for two reasons. First, increased exposure to allergens can exacerbate allergic reactions. Second, as we age, our skin thins and loses elasticity which makes us “more prone to water loss, dryness, and disruptions in the skin barrier,” Joshi says. These changes in the skin “allow allergens to enter into the skin easier and may increase the risk of developing sensitization,” he explains. “People tend to tolerate itchy skin, thinking it is a sign of aging,” says Garcia-Ibá?ez. However, he says that with the right diagnosis and treatment “patients can get better.”

6. Lifestyle changes

Sometimes lifestyle changes cause allergies to surface for the first time in adulthood. Getting a new pet, moving, traveling to a new geographic location, or trying new products for the first time can all cause adults to develop new allergies. Garcia-Ibá?ez says that he sees new allergies develop among patients who are new to the area where there might be different kinds of pollen, when they bring a pet into their home, and when they start using air conditioning for the first time.

When to see an allergist

The signs of adult-onset allergies aren’t always obvious, and they can easily be confused with other conditions. “One of the major symptoms many people overlook is poor quality sleep. If someone is waking up tired in the morning, I always suggest they are evaluated for allergies,” says Soffer.

According to Joshi, other things to look out for are sneezing, itchy or watery eyes, nasal congestion, a runny nose, difficulty breathing, coughing and difficulty concentrating. Although many of these symptoms overlap with COVID-19 and the common cold, Joshi says that “allergies generally last longer and are associated with more sneezing and itchiness of the nose, eyes, and ears.” He adds that if symptoms recur during a specific season each year, then allergies are the more likely diagnosis — even if occurring for the first time as an adult.