What Is an Allergy?

Ages 3-5 Simple Explanation

You know how your body has helpers inside it that fight off germs to keep you healthy? Those helpers are really good at their job! But sometimes, those helpers get confused. They see something that isn't actually dangerous — like a tiny bit of peanut or some fluffy cat fur — and they think it's a germ trying to hurt you.

When your body's helpers get confused and start fighting something harmless, that's called an allergy. Your body might start sneezing, or you might get itchy, or your nose might get stuffy. These things happen because your body is trying to fight off something it thinks is bad, even though it's really not.

Different people are allergic to different things. Some kids are allergic to certain foods, like milk or peanuts. Some kids are allergic to things in the air, like flower dust called pollen. Some kids are allergic to animal fur. And some kids don't have any allergies at all!

If you have an allergy, that's okay! Lots of kids do. Your doctor and your parents know how to help keep you safe. Sometimes you take medicine that helps your body calm down, and sometimes you just stay away from the thing that makes you feel yucky. Your school knows about your allergies too, so they can help keep you safe.

Ages 6-8 More Detail

Your body has an immune system that works like a security guard — it watches for dangerous things like germs and fights them off to keep you healthy. An allergy happens when your immune system makes a mistake. It sees something perfectly safe, like peanut butter or cat hair, and thinks it's dangerous. So it launches a big fight against it, and that fight is what causes your allergy symptoms.

Allergy symptoms depend on what you're allergic to and how your body reacts. Pollen and dust allergies usually cause sneezing, a runny nose, and itchy, watery eyes. Food allergies can cause hives, stomach pain, or swelling. Some people get itchy skin rashes from touching certain things. The symptoms are your body's way of trying to get rid of the thing it thinks is harmful.

The things that trigger allergies are called allergens. Common allergens include pollen from trees and grass, dust, mold, pet fur, insect stings, and certain foods like peanuts, tree nuts, milk, eggs, and shellfish. You can be allergic to just one thing or several things. Allergies often run in families, so if your parents have allergies, you're more likely to have them too.

Food allergies at school are something to take seriously. If a classmate has a food allergy, being careful about what foods you bring near them isn't just being nice — it's keeping them safe. For some kids, even a tiny amount of the food they're allergic to can make them really sick. That's why some classrooms have rules about certain foods.

If you have allergies, your doctor can help. Allergy medicine can reduce symptoms like sneezing and itching. For some allergies, doctors can do allergy shots over time that help your body learn to stop overreacting. And for serious food allergies, carrying an EpiPen — a special medicine that stops a severe reaction — is really important. Allergies can be annoying, but they don't have to stop you from doing the things you love.

Ages 9-12 Full Explanation

An allergy is an overreaction by your immune system to a substance that's normally harmless. When your body encounters something you're allergic to — called an allergen — your immune system treats it like a serious threat, even though it's actually safe. It releases chemicals to fight off the invader, and those chemicals are what cause all your allergy symptoms.

The main chemical your body releases during an allergic reaction is called histamine. Histamine causes blood vessels to swell, which leads to a stuffy nose. It triggers mucus production, giving you a runny nose. It irritates nerve endings, making things itchy. It can cause the airways in your lungs to tighten, making breathing harder. This is why allergy medicines are called antihistamines — they block the effects of histamine.

Allergies show up in different forms depending on the allergen. Seasonal allergies, sometimes called hay fever, happen when pollen from trees, grasses, or weeds is in the air — that's why they're worst in spring and fall. Year-round allergies can be triggered by things like dust mites, mold, or pet dander. Food allergies cause reactions when you eat specific foods. Contact allergies cause skin reactions when certain substances touch your skin, like poison ivy.

Severe allergic reactions, called anaphylaxis, are rare but serious. During anaphylaxis, the reaction affects the whole body — throat swelling can make it hard to breathe, blood pressure can drop, and dizziness or fainting can occur. This is a medical emergency, which is why people with severe allergies carry an epinephrine auto-injector (EpiPen). The epinephrine quickly reverses the reaction. If you see someone having a severe allergic reaction, find an adult immediately.

Food allergies are especially important to understand at school. When a classmate has a serious food allergy, keeping that food away from them is a matter of safety, not just preference. Some reactions can be triggered by very tiny amounts — even traces left on a desk or shared equipment. Respecting allergy rules in your classroom or cafeteria, washing your hands after eating, and not sharing food without checking are all simple things that help keep everyone safe.

If you have allergies, working with your doctor is the best approach. They can do tests to identify exactly what you're allergic to. For seasonal and environmental allergies, daily antihistamine medicine and avoiding triggers can make a big difference. For some allergies, immunotherapy — a series of gradually increasing exposures — can train your body to stop overreacting over time. And for food allergies, avoidance is key, along with always having your emergency medicine nearby just in case.