Pets
Pet animals, especially dogs and cats can cause asthma in sensitive people. Most breeds of dogs and cats are covered with fur. When the pets rub against your body or lick you, they shed saliva, fur and tiny flakes of skin (called dander). Some breeds of cats and dogs shed clumps of fur almost throughout the year. The sticky saliva dropped by these pets all over the house holds together the fur and dander. Also, when the pets are out of doors, pollen and fungus spores get stuck to their fur, and they carry these back into the house. The fur, dander, pollen or fungus spores can all trigger off symptoms of asthmaIf you are sensitive to dander, even a slight exposure to it can cause narrowing of the airways. However clean the house may look, the dander remains inside. The dander of cats is especially dangerous because it remains in the air for up to several months along with household dust. Thus, even if you do not go near the pets, or have given them away, you will still suffer from symptom of asthma for as long as the dander remains in the house.
It is important to remember that you can develop symptoms of asthma even from tiny particles of fur, wool, feather that may be released from pillows, clothes or bedding.
Pollen and fungus: If your symptoms of asthma occur more frequently in some particular season, it means that you are sensitive to pollen and fungi. Fungi (or moulds) are tiny plants that grow in damp and dark places. When they multiply, they release spores in the air. Pollen grains are tiny particles released by flowers when they bloom. They are very light and therefore travel for several miles with the wind. Many people outgrow their sensitivity to pollen, as they grow older. Pollen grains of common garden flowers such as roses, marigold, etc, do not cause asthma as they cannot float in the air because of being heavy, large and sticky.
Fungus spores can enter your house along with the wind and settle on household articles. They may be present all over, for example, on your bed, mattress, on or below the furniture, cushions, etc. The spores live for a long time in damp places, because they need moisture to grow. They, therefore, live longer in bathrooms, toilets, basements, air conditioners, coolers, humidifiers, etc.
However reduction of moisture is not good for asthma. Dry air can irritate the airways and also lead to symptoms of asthma.
Dust mites: Dust mites are the commonest cause of asthma all over the world. These are microscopic insects. The feces of dust mites cause allergy. A very strong coating of protein covers each round particle of feces. It is this protein which causes allergic reactions. When the mites die, their decomposed bodies combine with the household dust and cause allergic reactions.
Just like animals, human beings also shed dander, tiny flakes of skin. The dust mites feed on the dander that you shed everyday. Maximum amount of the dander shed by you is present on the bed sheets. Mites are commonly found on bed sheets, pillows mattresses, etc. They live in upholstered furniture, curtains, towels, clothes, stuffed animals, carpets, etc.
Allergy to dust mites is more common in cities and developed countries. This is because modern housing and use of insulation techniques enable the mites to thrive better. Also, many buildings in cities do not allow free flow of air.
Cockroaches: Allergy to cockroaches is very common. It may either be due to cockroach eggs, droppings or decomposed body parts. Cockroach remains are difficult to remove from the house. Even after you have managed to get rid of the cockroaches from the house, their microscopic decomposed body parts, droppings, etc, can still remain for several weeks.