You have an allergy when your body overreacts to things that don’t cause problems for most people. These things are called allergens. If you have allergies, your body releases chemicals when you are exposed to an allergen. One type of chemical that your body releases is called histamine. Histamineis your body’s defense against the allergen. The release of histamine causes your symptoms.
Hay fever is an allergic reaction to pollen. Pollen comes from flowering trees, grass, and weeds. If you are allergic to pollen, you will notice your symptoms are worse on hot, dry days when wind carries the pollen. On rainy days, pollen often is washed to the ground, which means you are less likely to breathe it.
- Allergies that occur in the spring (late April and May) are often due to tree pollen.
- Allergies that occur in the summer (late May to mid-July) are often due to grass and weed pollen.
- Allergies that occur in the fall (late August to the first frost) are often due to ragweed.
Allergens that can cause perennial allergic rhinitis include:
- Mold. Mold is common where water tends to collect, such as shower curtains and damp basements. It can also be found in rotting logs, hay, and mulch. This allergy is usually worse during humid and rainy weather.
- Animal dander.Proteins found in the skin, saliva, and urine of furry pets such as cats and dogs are allergens. You can be exposed to dander when handling an animal or from house dust that contains dander.
- Dust. Many allergens, including dust mites, are in dust. Dust mites are tiny living creatures found in bedding, mattresses, carpeting, and upholstered furniture. They live on dead skin cells and other things found in house dust.