If you’re sneezy or stuffy, you’re likely to blame a seasonal cold or deduce that an allergen like ragweed must be blooming, releasing its pesky pollen in the air and wreaking havoc on your sinuses. But if your congestion doesn’t subside and you feel like you’re single-handedly keeping Kleenex in business, there could be something deeper at play that has nothing to do with what’s in bloom. In fact, everything from gut imbalances and vitamin deficiencies to a hard-to-diagnose histamine intolerance could be to blame for your persistent sniffles. Ahead, naturopathic doctors and a registered dietitian share five possible reasons why you feel congested 24/7, and what to do about each of them.

1. Histamine Intolerance 

Histamine is a compound that the immune system produces when your body is having an allergic reaction, explains board-certified naturopathic doctor Dr. Lana Butner, N.D., founder of Dr. Lana Wellness. “Having too much histamine in the body can cause the immune system to think it needs to elicit an immune response to an allergy,” she says. 

This can be a problem when an enzyme called diamine oxidase (DAO), which is responsible for degrading histamine within the intestines, doesn’t function properly and histamine remains in the body in higher concentrations than it should, Butner says. “High concentrations of histamine can cause symptoms such as diarrhea, bloating, constipation, abdominal pain, headaches, dizziness, and, you guessed it, nasal congestion,” she explains.

But where does all of that histamine come from? Several foods are naturally high in histamine while others help release histamine stored in the body. Foods high in histamine include fermented foods, canned foods, acidic foods such as tomatoes and citrus fruits, avocado, dried fruits, mushrooms, smoked fish, anything that contains vinegar, pickled foods, yogurt, and spicy foods, Butner says. Meanwhile, foods that trigger histamine release include alcohol, bananas, papaya, citrus, chocolate, and wheat germ.

Solve it: Since there’s no specific diagnostic test at this time to clinically diagnose histamine intolerance, it is oftentimes considered after ruling out allergies or other conditions. Since high-histamine foods are pretty wide-ranging, many people struggle to pinpoint that their symptoms are, in fact, due to high levels of histamine.

If you get to that point, your solution is to stick to low-histamine foods and avoid high-histamine foods, Butner says. If that is not possible for you, you can take DAO supplements when eating high histamine or histamine-stimulating foods.

2. Mold Exposure

At the very least, mold exposure can cause chronic nasal congestion because the spores that mold overgrowth releases into the air irritate the linings of your sinus cavities and your throat, according to Dr. Revée Barbour, N.D., M.S., a licensed naturopath based in Sacramento. On top of congestion, exposure can also lead to debilitating symptoms, including fatigue, brain fog, muscle and joint pain, sleep disturbances, and other inflammatory conditions. In some people, mold can even cause Mast Cell Activation Syndrome, a condition that causes repeated episodes of anaphylaxis (a serious allergic reaction). 

If you get a whiff of mildew anywhere in your home, beware. Places that could potentially be damp or moist—think leaky pipes, drainage spots where water could pool, or leaks in the roof—are some of the most hospitable to mold growth, Barbour says.

Solve it: Have your home tested by certified indoor environmental mold specialists to confirm if there is an overgrowth present—especially if you’ve experienced flooding or leakage. If your home tests positive, you’ll consult with them about mold remediation. You’ll also want to contact your doctor so you can complete mold allergy testing and discuss treatment to help resolve your symptoms. 

Unfortunately, treating mold illness isn’t a quick fix. In addition to in-home mold remediation, some initial treatments may include nasal sprays containing saline and xylitol, as well as mycotoxin binders that prevent the toxic compounds produced by mold from being absorbed in the gut and bloodstream, says Barbour. A low-histamine diet, sauna therapy, and pulsed electromagnetic field (PEMF) therapy may also be among some initial treatments, he says. Because mold-related issues can be varied and severe, work with a doctor who specializes in mold illness to ensure proper treatment.

3. Micronutrient Deficiencies

Vitamins, minerals, and other nutrients help support our immune and respiratory function, so certain deficiencies may leave you feeling less than your best in those areas, Barbour explains. Specifically, vitamin D deficiency has been linked to chronic congestion. 

Read More: 7 Groups Of People Who May Need More Vitamin D

Solve it: Barbour recommends having your vitamin D levels checked by your doctor and consulting with them or a dietitian on how to raise your levels and restore balance. Ideally, you’d get vitamin D from sun exposure (it’s pretty tough to find in foods). But if you’re not getting enough rays, you could benefit from vitamin D supplements.

4. Gut Imbalances 

Sure, you know that gut microbiome imbalances can cause digestive issues—but they can also contribute to your pesky congestion. When good bacteria are reduced in our body from exposure to stress, a poor diet, antibiotics, or other reasons, microbial imbalances are created, he explains. “Then this reduces our overall immune protection and can promote harmful bacteria overgrowths linked to numerous health issues, including congestion,” Barbour says.

Read More: 6 Things We Do That Mess With Our Gut Microbiome

In fact, if you’re experiencing chronic congestion along with digestive issues like frequent bloating and irregularity, bad breath that’s not solved by brushing your teeth and regular dental visits, and strong cravings for sugary foods, your gut microbiome is likely off-kilter, he explains. 

Solve it: If you think your gut is the reason for your stuffy nose, start by reducing or eliminating your intake of potentially mucus-producing foods such as dairy, refined sugar, gluten, red meat, and alcohol, Barbour suggests. Instead, opt for foods that are high in antioxidants, micronutrients and fiber, such as fresh fruits and vegetables, fermented foods, beans, and gluten-free grains. You might also consider incorporating broad-spectrum probiotics to support those good gut bugs, he says.

5. Inflammatory Foods

Eating inflammatory foods (think anything heavily processed, including white bread, pastries, candy, and more) can also cause congestion, Butner says. You see, these foods raise levels of inflammation markers in the body, which the body responds to with an immune response, she explains. This response typically involves mucus production and, therefore, nasal congestion.

Solve it: Keeping a food journal that includes how you feel after eating certain foods could help you pinpoint whether inflammatory foods are to blame for your stuffy nose, Butner suggests. Pay attention to what you’re drinking, too, as soda and other sugary drinks can also cause inflammation, according to Harvard Health. Incorporating more known anti-inflammatory foods like fatty fish, leafy greens, and berries is also a good move.