What Causes Allergies?

Allergy triggers can be anywhere. Some of the most common are pollen, ragweed, grass, pet dander, dust mites, and mold. People who have allergies have an immune system that is sensitive to one or more of these usually harmless things.

Allergens: The Invader

Normally your immune system targets and protects you against threats like viruses and bacteria. Here you can see some bacteria (pink) being surrounded. But if you're allergic to pollen, for example, your immune system sees pollen as a threat. So when you're exposed to pollen, your immune system is ready to fight.

What Triggers an Allergy

It’s easy to come in contact with allergens. Chasing after dust bunnies, playing with your pet, or just walking out the door during allergy season can do it. An allergic reaction is set in motion by touching, swallowing, or inhaling an allergen.

Your Immune System Reacts

Once an allergen, such as pollen, enters your body, your immune system reacts and starts making antibodies. The antibodies help look for and then get rid of the pollen.

Allergic Response: Histamine Release

When antibodies find an allergen, they alert mast cells. These blood cells release chemicals such as histamine. These chemicals cause inflammation. Tissue around small blood vessels tightens. Fluid escapes. That's how you end up with a runny nose, swelling in your nasal passages, and congestion.

What Causes Allergies?

Allergies usually run in families. When both parents have allergies, their child’s chance is 75%. When one parent has allergies, the child’s chances are about 1 in 3. What you are allergic to also depends on your exposure to triggers. Some allergies can take years to develop.

Preventing Allergies

Avoid triggers when you can. Check pollen or mold reports before going outside. If levels are high, think about wearing a mask. During allergy season, shower before going to bed so you don't sleep with pollen in your hair. Keep windows closed and run the air conditioner. Vacuuming twice a week can help cut down on allergens.

Treating Allergies

Over-the-counter medications such as antihistamines, decongestants, eye drops, and nasal sprays also may help control symptoms and give you allergy relief. Talk with your pharmacist or doctor about which might help you.

When to See an Allergist

If you don’t know what’s causing your allergies, or if they’re severe, an allergy doctor can help. An allergist or immunologist will take your medical history and may do allergy tests. Tests expose you to possible allergens to see which ones cause a reaction. Depending on your allergies, your doctor may suggest prescription medications or allergy shots.

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