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.

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

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.

Everyone’s signs and symptoms of an allergic reaction are different. Read more about allergy symptoms and what might cause them.

Allergies on skin

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

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

Contact dermatitis, however, is the result of your skin coming into direct contact with an allergen. This could happen if you touch something you’re allergic to, such as a cleaning product or plant.

Types of skin allergies include:

  • Rashes. Areas of skin are irritated, red, or swollen, and can be painful or itchy.
  • Eczema. Patches of skin become inflamed and can itch and bleed.
  • Contact dermatitis. Red, itchy patches of skin develop almost immediately after contact with an allergen.
  • Sore throat. Pharynx or throat is irritated or inflamed.
  • Hives. Red, itchy, and raised welts of various sizes and shapes develop on the surface of the skin.
  • Swollen eyes. Eyes may be watery or itchy and look “puffy.”
  • Itching. There’s irritation or inflammation in the skin.
  • Burning. Skin inflammation leads to discomfort and stinging sensations on the skin.

Rashes are one of the most common symptoms of a skin allergy. Find out how to identify rashes and how to treat them.

Causes of allergies

Researchers aren’t exactly sure why the immune system causes an allergic reaction when a normally harmless foreign substance enters the body.

Allergies have a genetic component. This means parents can pass them down to their children. However, only a general susceptibility to allergic reaction is genetic. Specific allergies aren’t passed down. For instance, if your mother is allergic to shellfish, it doesn’t necessarily mean that you’ll be, too.

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.
  • Plants. Pollens from grass, weeds, and trees, as well as 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 like nickel are also common allergens.

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

  • itchy eyes
  • watery eyes
  • runny nose
  • coughing

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

Allergy treatments

The best way to avoid allergies is to stay away from whatever triggers the reaction. If that’s not possible, there are treatment options available.

Allergy treatment often includes medications like antihistamines to control symptoms. The medication can be over the counter or prescription. What your doctor recommends depends on the severity of your allergies.

Allergy medications include:


Many people opt for immunotherapy. This involves several injections over the course of a few years to help the body get used to your allergy. Successful immunotherapy can prevent allergy symptoms from returning.

Emergency epinephrine
If you have a severe, life-threatening allergy, carry an emergency epinephrine shot. The shot counters allergic reactions until medical help arrives. Common brands of this treatment include EpiPen and Twinject.

Some allergic responses are a medical emergency. Prepare for these emergency situations by knowing allergic reaction first aid.

Natural remedies for allergies

Many natural remedies and supplements are marketed as a treatment and even a way to prevent allergies. Discuss these with your doctor before trying them. Some natural treatments may actually contain other allergens and make your symptoms worse.

For example, some dried teas use flowers and plants that are closely related to plants that might be causing you serious sneezing. The same is true for essential oils. Some people use these oils to relieve common symptoms of allergies, but essential oils still contain ingredients that can cause allergies.

Each type of allergy has a host of natural remedies that may help speed up recovery. There are also natural options for children’s allergies, too.

How allergies are diagnosed

Your doctor can diagnose allergies in several ways.

First, your doctor will ask about your symptoms and perform a physical exam. They’ll ask about anything unusual you may have eaten recently and any substances you may have come in contact with. For example, if you have a rash on your hands, your doctor may ask if you put on latex gloves recently.

Lastly, a blood test and skin test can confirm or diagnose allergens your doctor suspects you have.

Allergy blood test

Your doctor may order a blood test. Your blood will be tested for the presence of allergy-causing antibodies called immunoglobulin E (IgE). These are cells that react to allergens. Your doctor will use a blood test to confirm a diagnosis if they’re worried about the potential for a severe allergic reaction.

Skin test
Your doctor may also refer you to an allergist for testing and treatment. A skin test is a common type of allergy test carried out by an allergist.

During this test, your skin is pricked or scratched with small needles containing potential allergens. Your skin’s reaction is documented. If you’re allergic to a particular substance, your skin will become red and inflamed.

Different tests may be needed to diagnose all your potential allergies. Start here to get a better understanding of how allergy testing works.

Preventing symptoms

There’s no way to prevent allergies. But there are ways to prevent the symptoms from occurring. The best way to prevent allergy symptoms is to avoid the allergens that trigger them.

Avoidance is the most effective way to prevent food allergy symptoms. An elimination diet can help you determine the cause of your allergies so you know how to avoid them. To help you avoid food allergens, thoroughly read food labels and ask questions while dining out.

Preventing seasonal, contact, and other allergies comes down to knowing where the allergens are located and how to avoid them. If you’re allergic to dust, for example, you can help reduce symptoms by installing proper air filters in your home, getting your air ducts professionally cleaned, and dusting your home regularly.

Proper allergy testing can help you pinpoint your exact triggers, which makes them easier to avoid. These other tips can also help you avoid dangerous allergic reactions.

Complications of allergies

While you may think of allergies as those pesky sniffles and sneezes that come around every new season, some of these allergic reactions can actually be life-threatening.

Anaphylaxis, for example, is a serious reaction to the exposure of allergens. Most people associate anaphylaxis with food, but any allergen can cause the telltale signs:

  • suddenly narrowed airways
  • increased heart rate
  • possible swelling of the tongue and mouth

Asthma and allergies

Asthma is a common respiratory condition. It makes breathing more difficult and can narrow the air passageways in your lungs.

Asthma is closely related to allergies. Indeed, allergies can make existing asthma worse. It can also trigger asthma in a person who’s never had the condition.

When these conditions occur together, it’s a condition called allergy-induced asthma, or allergic asthma. Allergic asthma affects about 60 percent of people who have asthma in the United States, estimates the Allergy and Asthma Foundation of America.

Many people with allergies may develop asthma. Here’s how to recognize if it happens to you.

Allergies vs. cold

Runny nose, sneezing, and coughing are common symptoms of allergies. They also happen to be common symptoms of a cold and a sinus infection. Indeed, deciphering between the sometimes-generic symptoms can be difficult.

However, additional signs and symptoms of the conditions may help you distinguish between the three. For example, allergies can cause rashes on your skin and itchy eyes. The common cold can lead to body aches, even fever. A sinus infection typically produces thick, yellow discharge from your nose.

Allergies can impact your immune system for prolonged periods of time. When the immune system is compromised, it makes you more likely to pick up viruses you come into contact with. This includes the virus that causes the common cold.

In turn, having allergies actually increases your risk for having more colds. Identify the differences between the two common conditions with this helpful chart.

Allergy cough

Hay fever can produce symptoms that include sneezing, coughing, and a persistent, stubborn cough. It’s the result of your body’s overreaction to allergens. It isn’t contagious, but it can be miserable.

Unlike a chronic cough, a cough caused by allergies and hay fever is temporary. You may only experience the symptoms of this seasonal allergy during specific times of the year, when plants are first blooming.

Additionally, seasonal allergies can trigger asthma, and asthma can cause coughing. When a person with common seasonal allergies is exposed to an allergen, tightening airways can lead to a cough. Shortness of breath and chest tightening may also occur. Find out why hay fever coughs are typically worse at night and what you can do to ease them.

Allergies and bronchitis
Viruses or bacteria can cause bronchitis, or it can be the result of allergies. The first type, acute bronchitis, typically ends after several days or weeks. Chronic bronchitis, however, can linger for months, possibly longer. It may also return frequently.

Exposure to common allergens is the most common cause of chronic bronchitis. These allergens include:

  • cigarette smoke
  • air pollution
  • dust
  • pollen
  • chemical fumes

Unlike seasonal allergies, many of these allergens linger in environments like houses or offices. That can make chronic bronchitis more persistent and more likely to return.

A cough is the only common symptom between chronic and acute bronchitis. Learn the other symptoms of bronchitis so you can understand more clearly what you may have.

Allergies and babies

Skin allergies are more common in younger children today than they were just a few decades ago. However, skin allergies decrease as children grow older. Respiratory and food allergies become more common as children get older.

Common skin allergies on babies include:

  • Eczema. This is an inflammatory skin condition that causes red rashes that itch. These rashes may develop slowly but be persistent.
  • Allergic contact dermatitis. This type of skin allergy appears quickly, often immediately after your baby comes into contact with the irritant. More serious contact dermatitis can develop into painful blisters and cause skin cracking.
  • Hives. Hives are red bumps or raised areas of skin that develop after exposure to an allergen. They don’t become scaly and crack, but itching the hives may make the skin bleed.

Unusual rashes or hives on your baby’s body may alarm you. Understanding the difference in the type of skin allergies babies commonly experience can help you find a better treatment.

Living with allergies

Allergies are common and don’t have life-threatening consequences for most people. People who are at risk of anaphylaxis can learn how to manage their allergies and what to do in an emergency situation.

Most allergies are manageable with avoidance, medications, and lifestyle changes. Working with your doctor or allergist can help reduce any major complications and make life more enjoyable.

Can allergies cause a fever?

No, allergies can’t cause a fever.

What causes allergies?

Allergies develop when your immune system reacts to a foreign substance or protein.

Are allergies contagious?

No, allergies aren’t contagious. You can’t spread your allergies to another person.

How are allergies diagnosed?

If you think you have allergies, don’t wait to see if your symptoms go away. If your symptoms last longer than a week or two or tend to come back during certain times of the year, make an appointment with an allergist.

An allergist is a healthcare provider who specializes in allergies. They can help diagnose your allergies through tests.

How do I test for allergies?

There are different types of allergy tests. The most common allergy tests are skin prick tests and blood tests.

Skin prick (scratch) tests can identify the allergens that cause your allergy symptoms. An allergist will use a thin needle to prick your skin with a tiny amount of different possible allergens. They then check to see if your skin reacts to the allergen.

Blood (IgE) tests can also identify allergies. However, they’re not as sensitive as skin prick tests. Blood tests evaluate IgE antibodies that your immune system produces against a specific protein.

What is the best treatment for allergies?
Nasal steroid sprays are generally the most effective medication for people with allergic rhinitis symptoms. Antihistamines block some of the effects of histamine and may offer additional benefits. Immunotherapy helps create a tolerance to allergens and can improve many of the symptoms related to inhalant allergy exposure.

Remember, your body is unique. What over-the-counter or prescription medications work for one person may not work well for you.

Talk to a healthcare provider. They can help recommend the best treatment for you.

What can/can’t I eat/drink if I have food allergies?

If you have food allergies, avoid any products that contain the allergens. By law, manufacturers must include all ingredients on the label of packaged foods for sale in the United States.

You should also consider other possible food allergy exposures. Some nonfood items may contain food allergens, and labeling laws don’t apply to nonfood items.

During the manufacturing process, some food items share equipment or surfaces. Look for labels that state whether the product shared equipment with possible food allergens.

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