Can a Humidifier Make Allergies Worse

Can a Humidifier Make Allergies Worse?


Can a Humidifier Make Allergies Worse?

A humidifier can potentially exacerbate allergies if the increased moisture levels encourage mold, dust mite, and bacteria growth which can aggravate allergy symptoms. However, following key tips for proper use and maintenance can allow you to safely benefit from humidifiers without worsening allergies.

Humidifiers work by increasing moisture levels in dry indoor air. They produce cool mist or warm steam to raise low humidity typically caused by winter heating systems. While intended to relieve congestion, dry skin, and more, humidifiers can also promote allergy triggers if used improperly.

Intended Benefits Potential Drawbacks
  • Relieve nasal congestion
  • Soothe throat irritation
  • Hydrate dry, itchy skin
  • Lessen static electricity
  • Encourage mold growth
  • Promote dust mite populations
  • Allow bacteria buildup in water

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PureGuardian H5450BCA
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How Humidifiers Work

Humidifiers work by dispersing moisture into dry air to raise humidity levels. There are two main types:

  • Evaporative humidifiers use a wick filter to soak up water which a fan blows air through to produce cool mist.
  • Ultrasonic humidifiers use high-frequency vibrations to create micro-fine cool mist. Some also have heating elements for warm steam.

Both humidifier types can effectively counteract low humidity, typically ranging 10-20% in winter versus the ideal 30-50%. Dry air lacks sufficient moisture to keep nasal passages, throat, and skin optimally hydrated and healthy.

By adding moisture back into the air, humidifiers offer benefits like:

  • Relieving congestion and throat irritation
  • Preventing nosebleeds, cracked lips, and dry, itchy skin
  • Minimizing static electricity sparks and even wood furniture cracks
  • Helping houseplants thrive

However, increasing humidity also provides the perfect damp conditions for mold, dust mites, and bacteria to thrive. These common allergic triggers can worsen allergy symptoms if they multiply out of control.

Potential Drawbacks of Humidifiers

While intended to help alleviate winter ailments, humidifiers can also encourage growth of microbes that provoke allergies if care isn’t taken.

Mold Growth

Mold spores float invisibly in indoor air. When humidity levels rise over 50%, it creates an optimal environment for mold to actively grow on surfaces.

Excess moisture allows mold colonies to flourish in humidifier tanks and internal components. Mist dispersed into the air spreads mold spores which can be inhaled, provoking hay fever and asthma flare-ups.

According to the Asthma and Allergy Foundation of America, common indoor molds linked to allergy symptoms include:

  • Alternaria – found in soils, dead organic debris
  • Aspergillus – grows on building materials, textiles, foods
  • Cladosporium – common outdoor mold also found indoors
  • Penicillium – grows on wallpaper, carpet, fabrics

Dust Mites

Dust mites are microscopic insects that feed on flakes of dead skin shed in home environments. They thrive in humid conditions over 50%.

The damp air enables dust mites to reproduce rapidly. Their fecal droppings and remains contain proteins that can trigger allergic reactions in sensitized individuals.

Bacteria Growth

Standing water provides an ideal breeding ground for bacteria. In humid environments, bacteria can grow rapidly in stagnant tank water, especially if using tap water which contains minerals.

Bacteria present in mist dispersed into air can be inadvertently inhaled. This allows lung infections like humidifier fever.

One common bacterium, pseudomonas aeruginosa, causes respiratory infections and thrives in low-nutrient water sources like humidifiers.

So if humidifiers aren’t cleaned regularly and thoroughly, they can spread problematic microbes through the air and worsen allergies as a result.

Tips for Using Humidifiers Safely

Thankfully, with proper humidifier use and maintenance, you can enjoy their hydrating vapors without exacerbating allergies. Here are some key best practices:

Use Ultrasonic or Evaporative Models

Humidifiers that boil water can disperse mineral dust and microbes in the steam which may aggravate allergies.

Opt for ultrasonic or evaporative humidifiers which don’t require heat, filters or wicks that can become moldy.

Clean and Disinfect Regularly

Follow manufacturer guidelines for cleaning and disinfecting. Change water daily, scrub tanks and trays to remove film buildup, and disinfect with diluted bleach or vinegar.

This prevents microbes from multiplying and dispersing through mist output.

Use Distilled or Filtered Water

Avoid using straight tap water which contains minerals that leave white dust and accelerate bacteria growth.

Use distilled or filtered water to help minimize potential contaminants.

Monitor Humidity Levels

Use a hygrometer to keep track of humidity, ideally between 30-50%. Higher levels encourage mold growth.

Adjust humidifier output as needed to stay in the proper range. Run for fewer hours if humidity gets too high.

Allow Proper Air Circulation

Don’t block air flow around the humidifier so surfaces can dry properly. Stagnant moisture promotes microbe growth.

Allow at least a few inches of clearance on all sides for air to circulate.

Dry Out Between Uses

Give humidifiers time to dry out completely between uses to prevent slime film buildup inside tanks and trays. Thorough drying inhibits mold and bacteria growth.

Replace Filters Regularly

For humidifiers with filters, be diligent about replacement schedules. Old, damp filters provide a breeding ground for microbes.

Look for UVC Light

Some humidifiers incorporate an ultraviolet C (UVC) light which helps kill bacteria, viruses and mold spores in the water. This adds an extra level of protection against microbes.

Use a Dehumidifier If Needed

If humidity levels exceed 50% and promote mold growth, use a dehumidifier to remove excess moisture from indoor air. Keeping humidity in check deters microbes.

High-Quality Humidifier Recommendations

When shopping for an effective yet allergy-friendly humidifier, look for these key features:

  • Ultrasonic or evaporative technology (no heat or wicks)
  • Large, easy to clean tanks and trays
  • Dishwasher-safe parts for easy disinfecting
  • Removable humidity sensor for accuracy
  • UVC light for reducing microbes
  • Auto shut-off when empty


While humidifiers can encourage allergy triggers like mold, dust mites and bacteria, following best practices for humidifier use allows you to safely increase moisture levels without exacerbating allergies.

Choose quality ultrasonic or evaporative models. Be diligent about frequent cleaning and disinfecting, use filtered water, monitor humidity levels, and ensure sufficient airflow around the unit. With proper maintenance, humidifiers can effectively provide hydration without worsening allergies.

Published by

Dennis Reed

Dennis Reed Owner and Author @