Seasonal allergens are back. Here's how you can fight them without unwanted medication side effects like weight gain and dry mouth.

• Allergy medication can be a helpful way to manage seasonal symptoms from pollen or mold.
• However, some medications have side effects ranging from sleepiness to urinary problems.

When there's a chill in the air, a sniffle, sneeze, or sore throat may be on the way, courtesy of clouds of pollen from autumn-loving weeds, or mold hiding in technicolored piles of fallen leaves.

To prevent seasonal allergies from derailing your autumn plans, it's important to know how to find the right medication and treatment, according to Dr. Purvi Parikh, an allergist and immunologist with the Allergy & Asthma Network.

The first step is knowing whether the symptoms you're experiencing are from allergies or from an illness like COVID-19, a cold, or the flu.

Allergies tend to be associated with itchiness, as well as long-lasting symptoms. In contrast, a fever, lots of mucus, and a sudden onset of symptoms is more indicative of a viral infection, Parikh said.

"Many symptoms, however, are identical like coughing, wheezing, stuffy nose, sneezing, sore throat so if you aren't sure — get tested for COVID and/or flu," she told Insider.

Once you've ruled out other illnesses, there are a wide variety of allergy medications to choose from, but some can cause side effects of their own, including dry mouth, drowsiness, or lesser-known symptoms like weight gain and insomnia.

Both insomnia and drowsiness can be side effects of allergy meds

Some medications can make you sleepy because of how they affect the brain.

Allergy medications are antihistamines, which means they work by blocking a chemical called histamine which is produced in response to the immune system sounding the alarm, according to the Cleveland Clinic. When you have an allergic reaction, your body is producing too much histamine in response to the perceived threat (such as pollen), causing symptoms like runny nose and other issues.

Some types of medications effectively block the symptom-causing histamine, but also affect the histamine receptors that regulate the sleep-wake cycle, resulting in drowsiness. These include diphenhydramine (better known as Benadryl).

Other antihistamines are less likely to cause drowsiness, including loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra).

However, some formulations (typically identified with a "D" after the name, such as Claritin D) contain a decongestant called pseudoephedrine, which has stimulant effects and may cause difficulty sleeping.

Some older allergy medications are linked to weight gain

A significant percentage of people with obesity are on medications that cause weight gain, according to Dr. Scott Isaacs, an endocrinologist and obesity medicine specialist.

That includes some antihistamines, he previously told Insider.

"The sleepier ones tend to cause more weight gain," he said.

"These side effects have been reported from older antihistamines like Benadryl because of its effects on the brain," Parikh said. But she noted these effects are rare.

Newer-generation medications are less likely to have weight gain as a symptom because they don't have as much of an effect on the brain, according to Parikh.

Claritin is least likely to cause weight gain, Isaacs said.

Dry mouth can be a side effect of allergy medications

One surprising side effect associated with some allergy medications is dry mouth, according to Parikh.

It can be uncomfortable, but can be managed by drinking plenty of water, sucking on ice cubes or sugar-free candy, chewing gum, or using special mouthwash or toothpaste, according to the Cleveland Clinic.

Newer-generation antihistamines that don't cause drowsiness, such as Claritin, Allegra, and Zyrtec, are less likely to cause dryness, too, Parikh said.

Allergy meds can sometimes worsen underlying bladder issues

In some cases, antihistamines can cause difficulty urinating if you have other bladder-related issues, according to Parikh.

If you notice persistent issues from a specific allergy medication, consider trying a different variety, she said.

"If side effects are severe you should switch as you may tolerate a different medication better," Parikh said.

You can ease or prevent allergy symptoms without medication, too

Some simple strategies can help to reduce pollen exposure, and therefore ease any allergic reaction to it, according to Parikh.

The two main culprits of fall allergies are ragweed, and mold growing on leaves, she said.

Both are outdoors, and so can be hard to avoid when you leave the house. However, pollen counts tend to be higher in the morning, Parikh said, so you can avoid the worst of it if you're able to stay indoors early in the day, and keep your windows closed.

When you do go outside, prevent pollen from coming home with you by washing off and changing into clean clothes when you return home, she said.

Sticking to general healthy habits can also help manage allergies, since factors like too little sleep, drinking alcohol, and smoking cigarettes can also worsen symptoms, Parikh said.

You can also use DIY methods to relieve allergy symptoms such as steam inhalation to help manage minor issues like congestion, but be wary of more severe symptoms like wheezing, coughing, or difficulty breathing.

"Any breathing symptom though please take it seriously and seek medical attention as this could be a sign of asthma which is dangerous or deadly if left untreated," Parikh said.