Why does it matter?

Global prevalence of mould allergy is estimated to be 3-10% in the general population. In England, approximately 2 million individuals reside in dwellings with considerable dampness and/or mould (3-4% of households).

It was discovered that a significant burden of respiratory diseases in England is due to residential dampness and mould, resulting in 2,800 Disability Adjusted Life Years lost in 2019. On the other hand, if we talk about Seasonal allergies and asthma create substantial health challenges, affecting approximately 10–30% of the world's population suffering from allergic rhinitis (or hay fever).^1–3

What are allergies?

An allergy occurs when your body's defence system (the immune system) mistakenly responds to substances that are typically harmless, such as dust, pollen, or specific foods. It considers these items hazardous, despite being harmless, leading to sneezing, itching, or other allergic reactions. The agents that trigger allergies are referred to as allergens. Examples include pollen, dust mites, mould, dander, and specific foods. Individuals who are easily affected by allergies are referred to as allergic or atopic (more likely to get allergies).⁴

Common symptoms include itching, flushing, rashes, hives, lip, tongue, and airway swelling (angioedema), nausea, vomiting, abdominal cramping, difficulty breathing, wheezing, bronchospasm, stridor, fainting, or collapse.⁵ 

Why it’s important to know the difference between mould and seasonal allergies

If you belong to the 20% of individuals who suffer from seasonal allergies (also known as hayfever), you’re well used to the itchy, watery eyes, congestion, runny nose, and scratchy throat that happen during spring and summer. However, your symptoms might not be caused by pollen, but rather by mould. Mould allergies produce symptoms similar to hayfever, but they usually occur at different times. Identifying the cause of your symptoms is essential for pursuing treatment.⁶

Mould allergy vs. seasonal allergies

What is a mould allergy?

A mould allergy is a reaction of the immune system when a person breathes in mould spores. Moulds are small fungi with airborne spores that drift through the atmosphere. They thrive in moist conditions and require four essentials for growth: nutrients, air, suitable temperature, and water. Moulds can be located outside, within residences, and in various structures. If you have a mould allergy, your immune system reacts excessively to certain mould spores, considering them as allergens. Inhaling mould spores prompts your immune system to activate symptoms like:

•  Sneezing
•  Itchy 
•  Watery eyes
•  Runny nose
• Nasal congestion, or
• Itching in the nose, mouth, and lips⁷

Mould allergy and asthma

If you have a mould allergy and asthma, exposure to mould spores can trigger your asthma symptoms. Some people experience severe asthma attacks after being exposed to specific moulds. The signs and symptoms of asthma include:

• Coughing and wheezing
• Shortness of breath
• Chest tightness⁸

What are the common types of moulds that cause allergies?

Although there are 100,000 distinct mould types, not everyone triggers allergy symptoms. Some of the most prevalent moulds that cause allergies are: Alternaria, Aspergillus, Cladosporium, and Penicillium.

An allergy to Aspergillus can be especially challenging for individuals with long-term lung conditions. A rare condition called allergic bronchopulmonary aspergillosis, or ABPA, results from a hypersensitivity to Aspergillus. ABPA affects about 1-2% of individuals who have asthma.⁹

Indoor mould

Indoor mould can grow on any organic surface and is found in damp areas such as:

• Basements
• Attics
• Under-sink cabinets
• Refrigerators
• Gcontainers
• Washing machines and clothes dryers
• Upholstery and house plants
• Dusty and musty old books, magazines, and newspapers
• Damp window mouldings and sills
• Shower stalls and shower curtains⁹

It can occur all year round (not just in one season)

In the United Kingdom, symptoms of mould allergy can arise at any time of the year since mould spores exist indoors and outdoors all year long. However, mould spore concentrations typically increase in late summer and fall, particularly during moist and warm conditions when outdoor mould flourishes on decomposing leaves and humid surroundings. Inside, mould exposure can last throughout the year in areas with humidity or inadequate airflow, like bathrooms or basements, causing mould allergies to be chronic for numerous individuals. This is different from seasonal allergies, such as pollen, which reach their highest levels in certain months during spring and summer.¹⁰

What are seasonal allergies?

Seasonal allergies, similar to other allergies, arise when the immune system reacts excessively to environmental triggers, typically in spring, summer, or fall when specific plants release pollen. In the UK, seasonal allergies are most commonly called hayfever or seasonal allergic rhinitis. They are usually allergic reactions triggered by pollen in the air released by trees, grass and weeds around the year.

Hayfever

Hayfever is a condition that is an allergy to grass or hay pollen. Pollen is the fine powder that plants, trees, or flowers generate in order to fertilise other plants, trees, or flowers of the same species. The most prevalent cause is grass pollen, which affects people every year between May and July (late spring to early summer). However, the word is frequently used to describe allergies induced by different pollen, such as tree pollen.

Tree pollens typically impact humans between March and May (early to late spring). Some people may be allergic to weed pollen (such as nettles and docks). Weeds often pollinate from early spring to early autumn.

Hayfever causes seasonal allergic rhinitis. This refers to nasal irritation (rhinitis) caused by an allergy (allergic), which typically happens at the same time or during the same season each year. It can also induce allergic inflammation of the eye's outer layers (allergic conjunctivitis).¹¹

Common characteristics of allergic rhinitis

Seasonal allergic rhinitis occurs at various periods of the year and is frequently linked to seasonal allergens such as pollen from trees, grasses, and weeds. Symptoms typically appear during seasons when certain allergens are prominent in the air. Hayfever is typically severe between late March and September, particularly when it is warm, humid, and windy. This is when the pollen counts are at their peak.

• Outdoor allergens induce symptoms
• Symptoms appear throughout various seasons
• Allergens such as tree pollen in the spring, grass pollen in the summer, and weed pollen in the autumn can induce symptoms
• Sneezing, a runny or stuffy nose, itchy/watery eyes, and itching of the throat or ears are common symptoms¹²

How do I distinguish between mould and seasonal allergy symptoms in my daily life?

Timing and seasonality

Seasonal allergies

Allergy symptoms usually manifest during certain seasons, based on the periods when allergens bloom or are released. For example, pollen allergies (like hayfever) are more common during seasons when certain plants emit pollen into the atmosphere. These symptoms often fluctuate in severity based on pollen levels, weather conditions, and various environmental influences.

Mould allergy

In comparison, signs of mould exposure can manifest as allergies throughout the year, since indoor mould development can continue in moist or humid conditions irrespective of the season.

These distinguishing symptoms can assist individuals and healthcare providers in differentiating mould exposure from seasonal allergies; however, certain symptoms such as nasal congestion, coughing, or watery eyes might overlap between both conditions.¹³

Location of symptoms

Mould allergies are often linked to indoor environments, particularly those with poor ventilation and water damage. Seasonal allergies are more likely to be triggered outside.

Diagnosis

Both mould allergy and seasonal allergy can be diagnosed by combining allergy testing and detailed medical history, and symptom evaluation.

Skin prick test

Allergen skin test. This test employs diluted levels of common or potential allergens, including moulds present in the surrounding environment. These substances are placed on your arm or back skin during the test through small punctures. If you have an allergy, a raised bump (hive) appears at the site of the test on your skin.

Blood test

A blood test, also known as a radioallergosorbent test, can assess your immune system's response to mold by determining the level of immunoglobulin E (IgE) antibodies in your circulation. A blood sample is sent to a medical laboratory and checked for mould sensitivity.¹⁴

Prevention tips

Mould allergy prevention tips

Lower your indoor humidity

Air cleaners and filters won't diminish mould spores if your house has more than normal humidity. Mould will flourish if indoor humidity exceeds 50%. Utilise a device known as a hygrometer to gauge the humidity levels inside your home. The aim is to maintain humidity levels ranging from 30 to 50%. Employ a dehumidifier to extract moisture and maintain indoor humidity levels under 50%.¹⁵

Use an air conditioner

Use an air conditioner. Mould spores can be trapped and prevented from flowing into your home using central air conditioning equipment equipped with a high-efficiency particulate air (HEPA) filter.

Fix leaks regularly

Repair the roof, do plumbing, and fix gutter leaks to stop mould from growing.

Reduce dampness

Avoid the use of carpeting in bathrooms as well as basements. If a spill occurs, dry it within 48 hours to prevent mould growth.

Seasonal allergy prevention tips

• Monitor pollen forecast: stay indoors, especially during peak pollen seasons (spring to fall)
• Keep windows and doors closed: use HEPA filters to reduce indoor pollen
• Use allergy medication as needed: to relieve both seasonal allergy as well as mould allergy, it is advised to take antihistamine medications, nasal sprays and decongestants

Summary

• Global prevalence of mould allergy is estimated to be 3-10% in the general population. On the other hand, if we talk about Seasonal allergies and asthma create substantial health challenges, affecting approximately 10–30% of the world's population suffering from allergic rhinitis (or hayfever)
• Although there are 100,000 distinct mould types, not everyone triggers allergy symptoms
• Seasonal allergic rhinitis occurs at various periods of the year and is frequently linked to seasonal allergens such as pollen from trees, grasses, and weeds
• To relieve both seasonal allergy as well as mould allergy, it is advised to take antihistamine medications, nasal sprays and decongestants