Indoor allergy refers to the allergic reaction associated with indoor allergens. Indoor allergens are usually harmless airborne substances witch can cause allergic reaction in sensitive persons. These substances are constitutional part of our living and working environment.

When we talk about allergies most people think about asthma or hay fever or some other outdoor allergies. And we think on food allergy or seasonal allergies.

Mostly we presume our home as a safe place where we can hide from allergies. But in reality our homes are full of allergens that are very difficult to avoid. And they are there to stay for the whole year.

Many allergens in your home can cause allergic symptoms, but the house dust is one of the main inducement of indoor allergies.
No matter how often you clean you home there will be some house dust present in it. It varies depending on different factors:
- type of construction of your home
- age of your home
- the temperature and humidity in the home
- what do you keep in the home (everything from objects, food, books, clothes to furniture)
- who lives in the home (human, pet animal, and plant) etc.

House dust is an airborne mixture that might contain fine particles of soil and plant material from indoors or outdoors, particles of human and animal skin (dander) and hair, fabric fibers, mold spores, dust mites, fragments of insects that have died and their waste, food particles, and other debris.
Although many substances in dust can trigger allergic symptoms, the most important indoor allergens are dust mites, pet dander, cockroaches, and molds.

The Enviromental Protection Agency (EPA) ranks indoor air pollution among the top five environmental risks to public health.
EPA studies indicate that indoor levels of many pollutants may be 25 times, and occasionally more than 100 times, higher than outdoor levels.
Most homes generate about 40 pounds of dust per year for every 1,500 square feet of space.
Reasearch shows that about 40,000 dust mites, a common cause of household allergies, can be found in only one ounce of dust.
It is suggested we have to drink approximately two quarts of clean water each day. By comparison, we inhale approximately 15,000 quarts of air each day.