Humidifier vs dehumidifier — we explain the difference and why you might have the wrong appliance

A humidifier in a bedroom
(Image credit: Getty Images)

At first glance, the difference between a humidifier vs dehumidifier might seem like two sides of the same coin, both designed to improve indoor air quality. However, these two helpful appliances serve opposite functions in your home. 

On one hand, humidifiers add moisture to the air, combating dry conditions that can lead to respiratory issues, skin irritation, and damage to timber structures. Dehumidifiers, in contrast, remove excess moisture, preventing damp and condensation, and creating a less hospitable environment for allergens, mould and mildew. 

So, how do you know if it's a humidifier or a dehumidifier you require? Keep reading to learn the key differences between these two appliances. 

Humidifier vs dehumidifier – what's the difference?

A humidifier’s primary function is to introduce moisture into the air, creating a more hospitable and health-friendly environment, particularly in settings where dry conditions prevail. Dry indoor air can lead to a slew of health issues and cause damage to your belongings, such as wooden furniture, instruments, and houseplants.   

On the flip side, a dehumidifier works by extracting moisture from the air, a crucial function in damp indoor spaces to prevent the growth of different types of mould and mildew. If your home suffers from dampness or condensation it's a dehumidifier you need (like the Probreeze 20L dehumidifier or the Meaco 20L low energy dehumidifier). Most homeowners will find themselves requiring a dehumidifier at some stage, especially during colder months.

What are the signs you need a humidifier? 

A dry and wilted houseplant in a terracotta pot

Houseplants going crispy despite frequently watering might be a sign that the air in your home is too dry.  (Image credit: Getty Images)

In conditions where the air is persistently dry, a humidifier like this deLonghi mini humidifier from Appliances Direct may be required. Indications that the air in your home is too dry include: 

  • Respiratory issues 
  • Dry eyes or throat 
  • Frequent static electricity
  • Cracking wooden furniture and fixings like solid oak doors
  • Wilting houseplants

In these scenarios, a humidifier can help restore your home to normal levels of humidity, creating a more comfortable living environment.

The downsides of a humidifier

While humidifiers offer numerous benefits, they are not without their potential downsides. If not cleaned regularly, they can become a breeding ground for mould and bacteria, which are then dispersed into the air, potentially leading to respiratory issues. Over-humidification can result in condensation, leading to mould growth on walls and other surfaces, and providing an ideal environment for dust mites. Proper maintenance, regular cleaning, and monitoring humidity levels are essential.

These are the signs you need a dehumidifier 

mould around windows

Mould and condensation are both signs you require a dehumidifier.  (Image credit: Getty Images)

While a humidifier increases levels of humidity in your home, a dehumidifier works by reducing humidity levels in your home. Signs that your humidity level is too high include: 

To accurately determine whether a dehumidifier is the right choice for your home, consider factors such as climate, season, and specific areas of your home. Basements, for instance, are prone to dampness and might benefit from a dehumidifier. 

  • A musty smell
  • Visible mould spots
  • Persistent condensation on windows 
  • A general feeling of dampness in the air

Humidifier vs dehumidifier – which is better for allergies?

modern dehumidifier in home office

Dehumidifiers can help reduce allergies caused by damp or mouldy conditions.  (Image credit: Duux)

If you’re experiencing persistent dry skin, nose bleeds, irritated eyes, or throat discomfort, these could be signs that your indoor air is too dry and you require a humidifier. A humidifier can also reduce the likelihood of nosebleeds and help alleviate symptoms of the flu or common cold. 

However, sometimes respiratory issues and allergies are actually indicators of damp and excess moisture in the air, not dry air. In such cases, a dehumidifier would help alleviate these issues more effectively than a humidifier.

A hygrometer, like this inexpensive ThermoPro hygrometer from Amazon, can be a useful tool in measuring indoor humidity levels, helping you maintain a normal level of humidity within the recommended range of 30% to 50%.

Choosing the right appliance has tangible benefits for both your health and comfort. You should purchase a dehumidifier if you want to help treat damp and prevent mould growth in your home. A humidifier is required for particularly dry conditions, and can soothe irritated skin and respiratory passages, as well as preserving the condition of your belongings.

Gabriella Dyson
Assistant Editor

Gabriella is Homebuilding & Renovating's Assistant Editor. She is a DIY enthusiast and a lover of all things interior design. She’s spent the past decade crafting copy for regional publications, award-winning architects, and leading UK homeware brands. 

She has a particular passion for historic buildings and listed properties, and she is currently in the process of renovating a Grade II-listed Victorian coach house in the West Country. At Homebuilding & Renovating Magazine, Gabriella is responsible for curating the magazine's home case studies and regularly contributes to the Homebuilding website.