An allergy is an immune system response to a foreign substance that’s not typically harmful to your body. These foreign substances are called allergens. They can include certain foods, pollen, or pet dander.

Your immune system’s job is to keep you healthy by fighting harmful pathogens. It does this by attacking anything it thinks could put your body in danger. Depending on the allergen, this response may involve inflammation, sneezing, or a host of other symptoms.

Your immune system normally adjusts to your environment. For example, when your body encounters something like pet dander, it should realize it’s harmless. In people with dander allergies, the immune system perceives it as an outside invader threatening the body and attacks it.

Symptoms of allergies

The symptoms you experience because of allergies are the result of several factors. These include the type of allergy you have and how severe the allergy is.

If you take any medication before an anticipated allergic response, you may still experience some of these symptoms, but they may be reduced.

For food allergies

Food allergies can trigger swelling, hives, nausea, fatigue, and more. It may take a while for a person to realize that they have a food allergy. If you have a serious reaction after a meal and you’re not sure why, see a medical professional immediately. They can find the exact cause of your reaction or refer you to a specialist.

For seasonal allergies

Hay fever symptoms can mimic those of a cold. They include congestion, runny nose, and swollen eyes. Most of the time, you can manage these symptoms at home using over-the-counter treatments. See your doctor if your symptoms become unmanageable.

For severe allergies

Severe allergies can cause anaphylaxis. This is a life-threatening emergency that can lead to breathing difficulties, lightheadedness, and loss of consciousness. If you’re experiencing these symptoms after coming in contact with a possible allergen, seek medical help immediately.

Causes of allergies

Common types of allergens include:

• Animal products. These include pet dander, dust mite waste, and cockroaches.
• Drugs. Penicillin and sulfa drugs are common triggers.
• Foods. Wheat, nuts, milk, shellfish, and egg allergies are common.
• Insect stings. These include bees, wasps, and mosquitoes.
• Mold. Airborne spores from mold can trigger a reaction.