About Mold & Mildew Allergies: Symptoms, Treatment & Prevention

What is Mold?

Mold and mildew are forms of fungi that multiply using airborne spores and are known to grow in damp areas². They can grow both inside and outside your home if it’s damp². They are often found on logs and leaves, in your basement, or even in the cabinet under your sink¹.

What’s the Difference Between Mold and Mildew?

Mildew is the name for certain kinds of mold or fungus⁵, usually describing a flat mold growth⁵. Molds can thrive on any organic material, whereas mildew often lives on shower walls and windowsills⁵.

Types of Mold

There are roughly 1,000 types of mold in the United States¹. But not all kinds will cause an allergic reaction, and being allergic to one type of mold doesn’t mean you’ll react badly to all of them³. Some of the most common types of mold that can cause allergies include⁴:

What Does Mold Look Like?

Different molds have different appearances and textures, but they often look like discoloration or stains on a surface – and are frequently mistaken for those very things.

Molds can come in a variety of colors, including:

Some will have a fuzzy or velvety texture that makes them easier to identify. Others can have a rough appearance instead.

What Does Mold Smell Like?

• Stale/musty – the most commonplace comparison is usually old socks or a stuffy attic

• Earthy – resembling a dense forest, or rotting wood

• Damp – similar to wet dog fur or a dank locker room

• Rotting/fermenting – like aging cheese or fermenting alcohol

• Tangy/sour – similar to a sweaty odor following an intense workout

None of these characteristics are pleasant, and as the mold spreads over time, the smell can get worse. These smells are caused by microbial volatile organic compounds (mVOCs), produced by mold, and released into the air.

When is Mold Allergy Season?

Mold allergy season isn’t simple to pin down, as different molds are active at different times of the year. Most outdoor molds are inactive during the winter, and are more active during the spring and fall as they thrive in moist environments and commonly grow on plants that the winter cold kills². Indoor molds, meanwhile, can develop at any time of year in damp bathrooms, kitchens or basements². In other words, there is no mold allergy season as such. Instead, understanding which mold you may be allergic to and learning when and where it is most common, is usually the best course of action.

Why Does Mold Cause Allergies?

If you have an allergy to mold, you may experience an allergic reaction to the mold spores in the air⁴. Similar to pollen and other airborne allergens, when mold spores are released, they are easily breathed in⁴ through the nose or mouth.

An allergic reaction to mold occurs when your body reacts to these mold spores as a threat, and fights back against the spores with an immune response⁴. Read on to learn about the symptoms that you may experience as a result of an allergic reaction to mold.

Mold & Mildew Allergy Symptoms

Mold and mildew allergy symptoms are often similar to the symptoms of hay fever. Allergic reactions to mold usually resemble seasonal allergies, and symptoms may include⁴

If you’re asthmatic, it’s possible that your mold allergy could also trigger an asthma attack⁴.

Mold & Mildew Allergy: Serious Symptoms

Sometimes, mold and mildew allergies can cause more serious symptoms, including⁴:

• Skin rash/hives

• Flu-like symptoms, including fever

• Feeling generally unwell

Mold & Mildew Allergy: Dangerous Symptoms

Occasionally, such allergies can have even more serious effects. Some molds and mildew can cause⁴:

• Lung infections

• Anaphylaxis (life-threatening lung issues)

Indoor vs. Outdoor Mold Allergy Symptoms

The mold allergy symptoms you experience will likely be the same regardless if they are caused by indoor or outdoor mold. The main difference between indoor and outdoor mold allergy symptoms is when you might experience them.

If your symptoms are triggered by indoor mold, you’ll likely experience symptoms throughout the year. You may also feel particularly bad after spending time indoors near mold growth.

If your symptoms are triggered by outdoor mold, it is likely that you will only experience symptoms during wetter seasons, like spring and fall, when the ground outside is damp enough for mold to grow. You may also feel worse after spending time outside when molds are growing and producing spores.

How to Prevent Mold Allergies

Wet or damp surfaces indoors – especially in bathrooms and basements – can attract mold and help it to spread.You can help prevent indoor mold allergies by finding and cleaning up existing mold and making it harder for mold to grow in your home – mainly by keeping surfaces dry⁴.

Top tips and tricks for preventing mold include⁴:

• Using a dehumidifier to keep humidity levels below 50%

• Removing indoor houseplants – or ensuring they stay free from mold growth

• Keeping your washing machine clean and dry when not in use

• Regularly cleaning and drying out damp cabinets – i.e. under your sinks

• Washing towels frequently and ensuring they dry fully

• Fixing leaky faucets and pipes

• Making sure rooms are properly ventilated

• Using a vented exhaust fan to remove excess moisture

• Using cleaning solutions designed to kill mold and mildew

You can also try to prevent or reduce outdoor mold allergy symptoms by staying indoors when mold counts are high. Keeping damp and decaying leaves and wood out of your front or back yard should also help to reduce the places mold can grow⁴.