Allergy

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Overview

Allergies are your body’s reaction to a normally harmless substance such as pollen, molds, animal dander, latex, certain foods and insect stings. Allergy symptoms range from mild – rash or hives, itchiness, runny nose, watery/red eyes – to life-threatening. Treatments include antihistamines, decongestants, nasal steroids, asthma medicines and immunotherapy.

Symptoms

Allergy symptoms, which depend on the substance involved, can affect your airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.

Hay fever, also called allergic rhinitis, can cause:

Sneezing

Itching of the nose, eyes or roof of the mouth

Runny, stuffy nose

Watery, red or swollen eyes (conjunctivitis)

A food allergy can cause:

Tingling in the mouth

Swelling of the lips, tongue, face or throat

Hives

Anaphylaxis

An insect sting allergy can cause:

A large area of swelling (edema) at the sting site

Itching or hives all over the body

Cough, chest tightness, wheezing or shortness of breath

Anaphylaxis

A drug allergy can cause:

Hives

Itchy skin

Rash

Facial swelling

Wheezing

Anaphylaxis

Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to:

Itch

Redden

Flake or peel

Anaphylaxis

Some types of allergies, including allergies to foods and insect stings, can trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, anaphylaxis can cause you to go into shock. Signs and symptoms of anaphylaxis include:

Loss of consciousness

A drop in blood pressure

Severe shortness of breath

Skin rash

Lightheadedness

A rapid, weak pulse

Nausea and vomiting

When to see a doctor

You might see a doctor if you have symptoms you think are caused by an allergy, and over-the-counter allergy medications don't provide enough relief. If you have symptoms after starting a new medication, call the doctor who prescribed it right away.

For a severe allergic reaction (anaphylaxis), call 911 or your local emergency number or seek emergency medical help. If you carry an epinephrine auto-injector (Auvi-Q, EpiPen, others), give yourself a shot right away.

Even if your symptoms improve after an epinephrine injection, you should go to the emergency department to make sure symptoms don't return when the effects of the injection wear off.

If you've had a severe allergy attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your doctor. Evaluation, diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a doctor who specializes in allergies and immunology.

Causes

Anything that you come into contact with that your body views as a “harmful invader” can be a cause of an allergy. Normally harmless substances that are common causes of allergies include pollen, animal dander, mold, dust, foods, insect venom and latex

Technically, your symptoms are the result of a chain of events that are your body’s response to the “harmful invader.” Your body “sees” the invader, makes antibodies to fight the invader, and in so doing, releases histamines that cause your allergy symptoms.

Airborne allergens, such as pollen, animal dander, dust mites and mold.

Certain foods, particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk.

Insect stings, such as from a bee or wasp.

Medications, particularly penicillin or penicillin-based antibiotics.

Risk factors

Host factors involved in the risk for allergy are heredity, sex, race and age, with heredity being by far the most important. Exposure to allergens has been identified as an influential environmental factor, whereas passive smoking and pollution may act as an adjuvant. The atopic mother may during pregnancy add to an atopy-prone environment. Whereas respiratory infections are associated with attacks of bronchial asthma, infections in early life might play a role in the protection against atopy by preferential stimulation of a Th1 response, with mutual down-regulation of the Th2 response.

Conclusion: Recognition of the risk factors for allergy is important in order to select the factors that could be modified for individuals at risk and in order to identify those factors of which the modulation could evolve in general preventive measures.

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Complications

Anaphylaxis. If you have severe allergies, you're at increased risk of this serious allergy-induced reaction. ...

Asthma. If you have an allergy, you're more likely to have asthma — an immune system reaction that affects the airways and breathing. ...

Sinusitis and infections of the ears or lungs.

Prevention

The best way to prevent an allergic reaction is to avoid the substance that you're allergic to, although this is not always easy or practical.

Below is some practical advice that should help you avoid the most common allergens.

House dust mites

One of the biggest causes of allergies are dust mites, which are tiny insects found in household dust.

You can limit the number of mites in your home by: 

choosing wood or hard vinyl floor coverings instead of a carpet

fitting roller blinds that can be easily wiped clean

choosing leather, plastic or vinyl furniture instead of upholstered furniture

cleaning cushions, soft toys, curtains and upholstered furniture regularly, either by washing (at a high temperature) or vacuuming

using tested allergy-proof covers on mattresses, duvets and pillows

using a vacuum cleaner fitted with a HEPA (high efficiency particulate air) filter, as it can trap more dust mites than ordinary vacuum cleaners

regularly wiping surfaces with a damp, clean cloth – avoid dry dusting, as this can spread dust into the air

Concentrate your efforts of controlling dust mites in the areas of your home where you spend the most time, such as the bedroom and living room.

You can find more information on allergies in the home on the Allergy UK website.

Pets

It's not pet fur that causes an allergic reaction. Instead, it's flakes of their dead skin, saliva and dried urine.

If you cannot permanently remove a pet from the house, you could try: 

keeping pets outside as much as possible, or limiting them to a particular area of the house, preferably an area without carpet

not allowing pets in bedrooms

washing pets at least once a week

regularly grooming pets outside

regularly washing all bedding and soft furnishings pets lie on

using an air filter in rooms where you spend most of your time

increasing ventilation with fans or air conditioning, or by opening windows

If you're visiting a friend or relative with a pet, ask them not to dust or vacuum on the day you're visiting, as this will stir up the allergens into the air.

Taking an antihistamine medicine about an hour before entering a pet-inhabited house can also help reduce your symptoms.

The Allergy UK website has more information about domestic pet allergies.

Mould spores

Tiny particles released by moulds can cause an allergic reaction in some people.

You can help prevent this by:

keeping your home dry and well ventilated

removing any indoor pot plants from your home

not drying clothes indoors, not storing clothes in damp cupboards, and avoiding packing clothes too tightly in wardrobes

dealing with any damp and condensation in your home

avoiding damp buildings, damp woods and rotten leaves, cut grass and compost heaps

Food allergies

By law, food manufacturers must clearly label any foods that contain something that's known to cause allergic reactions in some people.

By carefully checking the label for the list of ingredients, you should be able to avoid an allergic reaction.

People with food allergies most often experience an allergic reaction while eating out at a restaurant.

You can avoid this by:

not relying on the menu description alone (remember, many sauces or dressings could contain allergens)

communicating clearly with the waiting staff and asking for their advice

avoiding places where there's a chance that different types of food could come into contact with each other, such as buffets or bakeries

letting restaurant staff know your dietary requirements, including how severe your food allergy or intolerance is

always checking what allergens are in the dish, even if you have eaten it before, as recipes and ingredients can change

Remember, simple dishes are less likely to contain "hidden" ingredients. If you're not sure about a dish, do not risk it.

Read more about living with a food allergy and get advice from the Food Standards Agency on food allergen labelling.

Hay fever

Pollen allergies, more commonly known as hay fever, are caused when trees and grasses release pollen into the air.

Doctors often call hay fever allergic rhinitis. 

Different plants pollinate at different times of the year, so the months you get hay fever will depend on what sort of pollen you're allergic to.

Typically, people are affected during spring (trees) and summer (grasses).

To help keep your hay fever under control, you can:

check weather reports for the pollen count and stay indoors when it's high, if possible

avoid drying clothes and bedding outside when the pollen count is high

wear wraparound sunglasses to protect your eyes

keep doors and windows shut when possible

shower and change your clothes after being outside

avoid grassy areas, such as parks and fields, particularly in the early morning, evening or night, when the pollen count is highest

if you have a lawn, try asking someone else to cut the grass for you 

Find out how to prevent hay fever

Insect bites and stings

If you have ever suffered a bad reaction to an insect bite or sting, it's important to take precautions to minimise your risk.

When you're outdoors, particularly in the summer, you could:

cover exposed skin

wear shoes

apply insect repellent

avoid wearing strong perfumes or fragrances, as these can attract insects

Find out how to prevent insect bites and stings

Preventing severe allergies (anaphylaxis)

If you're at risk of experiencing a severe allergic reaction (anaphylaxis), make sure you carry 2 adrenaline auto-injectors with you everywhere.

Wearing a MedicAlert or Medi-Tag medallion or bracelet can make others aware of your allergy in an emergency.

Consider telling your teachers, work colleagues and friends so they can give you your adrenaline injection in an emergency while waiting for an ambulance.