People who have always kept cats suddenly become allergic to cats. This is called "allergy" or "hypersensitivity" in medicine. It refers to the body's immune system reacting to some non-harmful substances (such as pollen, animal fur, etc.) If it is too sensitive, an immune response will occur, causing harm to the body.

The skin rash and itching that people encounter every day is a kind of allergic reaction. Some people are congenitally allergic to certain substances, but have not been exposed to them, or have no allergic symptoms for the first time. Or they are not allergic to a certain substance, but due to changes in their own immune system, allergic reactions occur when they are exposed again. ​​​​​​

On the one hand, it is related to people’s own physical constitution, and they are prone to react to pet hair and dander. People with atopic constitution can be sensitized when they first come into contact with the antigen, but no clinical reaction will occur. This is why I haven’t had any allergies to pet hair before.

Since the immune system of the body is constantly changing, the sensitized body will react when it is exposed to the same antigen again. The time is variable. The faster one can occur within seconds after the next exposure, while the slower one can take several days. Even months or longer.

The hair and dander of domestic pets are very easy to cause allergies. If pets are not cleaned in time, mold and mites on the hair are also important allergens. It is recommended that pet owners clean, disinfect and kill their pets regularly to reduce the chance of allergies.