Allergens are substances that cause an allergic reaction in the body. There are many different types of allergens, such as foods, pet dander, pollen, and dust mites. Some common synonyms for the word allergen include irritant, antigen, stimulus, and trigger. These terms are often used interchangeably to describe substances that cause an allergic response. Additionally, allergens can be classified as environmental, seasonal, or occupational depending on where they are commonly found and how they affect individuals. It is important to identify and avoid allergens whenever possible to prevent allergic reactions and minimize the impact on an individual's quality of life.