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Everything you need to understand about allergies


An allergy is a reaction of the immune system to a foreign material that is not normally harmful to the body. These foreign substances are called allergens. This can include certain foods, pollen, or animal dander.

Your immune system's job is to keep you healthy by fighting harmful pathogens. To do this, it attacks anything it thinks might pose a threat to your body. Depending on the allergen, this reaction may be accompanied by inflammation, sneezing, or a number of other symptoms.

Normally, your immune system adapts to your environment. For example, when your body encounters something like animal dander, it should recognize that it's harmless. In people with dander allergies, the immune system perceives it as an outside invader that threatens the body and attacks it.

Allergies are common. Various treatments can help you avoid your symptoms.

Symptoms of allergies

The symptoms you experience due to allergies are the result of several factors. These include the type of allergy and the severity of the allergy.

If you are taking medication prior to an expected allergic reaction, some of these symptoms may still occur, but they may be reduced.

For food allergies

Food allergies can cause swelling, hives, nausea, fatigue and more. It may take a while for a person to realize they have a food allergy. If you experience a severe reaction after a meal and aren't sure why, you should see a doctor right away. He or she can find out the exact cause of your reaction or refer you to a specialist.

For seasonal allergies

Hay fever symptoms can resemble those of a cold. These include congestion, runny nose and puffy eyes. In most cases, you can treat these symptoms at home with over-the-counter remedies. See your doctor if symptoms become uncontrollable.

For severe allergies

Severe allergies can lead to anaphylaxis. This is a life-threatening emergency that can cause difficulty breathing, drowsiness, and loss of consciousness. If you experience these symptoms after coming into contact with a possible allergen, seek medical attention immediately.

The signs and symptoms of an allergic reaction are different for everyone. Read more about allergy symptoms and their possible triggers.

Allergies of the skin

Skin allergies can be a sign or symptom of an allergy. They can also be the direct result of exposure to an allergen.

For example, eating a food to which you are allergic may cause several symptoms. You may experience a tingling sensation in your mouth and throat. You may also develop a rash.

Contact dermatitis, on the other hand, occurs when your skin comes into direct contact with an allergen. This can happen when you touch something you are allergic to, such as a cleaning product or a plant.

Types of skin allergies include:

Skin rashes. The skin areas are irritated, red, or swollen and may be painful or itchy.

Eczema. The skin areas become inflamed and may itch and bleed.

Contact dermatitis. Red, itchy areas of skin appear almost immediately after contact with an allergen.

Throat inflammation. Throat or pharynx are irritated or inflamed.

Hives. Red, itchy, raised wheals of various sizes and shapes form on the skin surface.

Swollen eyes. The eyes may be watery or itchy and look "puffy."

Itching. The skin is irritated or inflamed.

Burning. Skin inflammation causes discomfort and burning sensations on the skin.

Rashes are one of the most common symptoms of skin allergy. Learn how to recognize rashes and how to treat them.

Causes of allergies

Researchers do not know exactly why the immune system triggers an allergic reaction when a normally harmless foreign substance enters the body.

Allergies have a genetic component. This means that parents can pass them on to their children. However, only a general susceptibility to allergic reactions is genetic. Specific allergies are not inherited. For example, if your mother is allergic to shellfish, it doesn't necessarily mean you will be too.

Common types of allergens are:

Animal products. These include animal dander, dust mites and cockroaches.

Medications. Penicillin and sulfa drugs are common triggers.

Foods. Allergies to wheat, nuts, milk, shellfish, and eggs are common.

Insect bites. These include bees, wasps, and mosquitoes.

Mold. Mold spores in the air can trigger a reaction.

Plants. Pollen from grasses, weeds and trees, and resin from plants such as poison ivy and poison oak are very common plant allergens.

Other allergens. Latex, often found in latex gloves and condoms, and metals such as nickel are also common allergens.

Seasonal allergies, also known as hay fever, are among the most common allergies. They are caused by pollen released by plants. They cause:

itchy eyes

watery eyes

runny nose


Food allergies are becoming more and more common. Learn about the most common types of food allergies and the symptoms they cause.

Treatment of allergies

The best way to avoid allergies is to stay away from the trigger of the reaction. If that's not possible, there are treatment options.


Treatment for allergies often includes medications such as antihistamines to control symptoms. These medications may be over-the-counter or prescription. What your doctor recommends depends on the severity of your allergy.