Overview

Allergies are an overreaction of the body's natural defence system that helps fight infections (immune system). The immune system normally protects the body from viruses and bacteria by producing antibodies to fight them. In an allergic reaction, the immune system starts to fight substances that are usually harmless, such as dust mites, pollen, or a medicine. It fights them as though these substances were trying to attack the body. This overreaction can cause a rash, itchy eyes, a runny nose, trouble breathing, nausea, and diarrhea.

An allergic reaction may not occur the first time you're exposed to an allergy-producing substance (allergen). For example, the first time you are stung by a bee, you may have only pain and redness from the sting. If you're stung again, you may have hives or trouble breathing. This is caused by the response of the immune system.

Many people will have some problem with allergies or allergic reactions at some point in their lives. Reactions can range from mild and annoying to sudden and life-threatening. Most allergic reactions are mild. Home treatment can relieve many of the symptoms. A reaction is more serious when a severe allergic reaction (anaphylaxis) occurs, when allergies cause other problems (such as nosebleeds, ear problems, wheezing, or coughing), or when home treatment doesn't help.

Allergies often occur along with other problems, such as asthma, ear infections, sinusitis, and sleep apnea.

Types of allergies

There are many types of allergies. Some of the more common ones include:

• Food allergies. They are more common in children than adults. Food allergies are most common in people who have an inherited tendency to develop allergic conditions. These people are more likely to have asthma and other allergies.
• Medicine allergies. Many prescription and non-prescription medicines can cause an allergic reaction. These reactions are common and unpredictable.
• Allergies to insect venom. When you are stung by an insect, poisons and other toxins in the insect's venom enter your skin. It's normal to have some swelling, redness, pain, and itching at the site of a sting. An allergic reaction to the sting occurs when your body's immune system overreacts to the venom of stinging insects.
• Allergies to animals. These are more likely to cause breathing problems than skin problems. You may be allergic to your pet's dead skin (dander), urine, dried saliva, or hair.
• Allergies to natural rubber (latex). Some people develop allergic reactions after repeated contact with latex, especially latex gloves.
• Allergies that develop from exposure to a particular inhaled substance in the workplace. These allergies may be called occupational asthma.
• Allergies to cosmetics, such as artificial nails, hair extensions, and henna tattoos.

Seasonal allergies show up at the same time of the year every year. They are caused by exposure to pollens from trees, grasses, or weeds.

Allergies that occur for more than 9 months out of the year are called perennial allergies.

Year-round symptoms (chronic allergies) can occur from exposure to animal dander, house dust, or mould.

Self-Care

Here are some things you can do at home to help your allergies.

• Avoid contact with whatever is causing the itching.

  If you know what's causing the itching or hives, then you can try to stay away from the irritant.

• Treat a sore throat.

  A sore throat may be caused by post-nasal drip. Adults and children who can gargle can try gargling with warm salt water at least once each hour to help ease throat soreness.

• Treat hay fever or seasonal allergies.

  Use saline washes to help clear a stuffy nose. Or take an allergy medicine that's specific to your symptoms.

• Look out for mould.

  Allergies that are worse in damp weather may be caused by mould. Mould produces spores that move, like pollen, in outdoor air during warmer months. During winter months, indoor moulds can also be a problem.

• Be aware of indoor allergies.

  Dust, vacuum, and mop often. Use HEPA filters on air cleaners and your vacuum. Clean or replace filters regularly.

  Wash sheets, pillowcases, and blankets weekly. Use detergent, hot or warm water, and a dryer if possible.

• Don't forget about animal allergies.

  When allergies are worse around pets or animals, symptoms may be caused by your pet's dead skin (dander), urine, dried saliva, or hair.

• Try antihistamines.

  An antihistamine medicine, such as loratadine (Claritin), may help relieve itching, redness, and swelling. Don't give antihistamines to your child unless you've checked with the doctor first. Be safe with medicines. Read and follow all instructions on the label.

• Try lotions or creams.

  Calamine lotion or hydrocortisone cream applied to the skin may help relieve itching.

When to call for help during self-care

Call 9-1-1 if any of the following occur during self-care at home:

• New or worse trouble breathing, wheezing, or tightness in the chest.
• New or worse swelling of the throat, tongue, lips, or mouth.

Call a doctor if any of the following occur during self-care at home:

• New or worse hives.
• New or worse skin swelling.
• New or worse belly pain, nausea, vomiting, or diarrhea.
• New or worse signs of infection, such as redness, warmth, pus, or a fever.
• Symptoms occur more often or are more severe.

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