The best way to prevent an allergic reaction is to avoid the allergen that causes it.

This is not always easy. Allergens such as house dust mites or fungal spores can be hard to spot and can breed in even the cleanest house.

It can also be hard to avoid pets, particularly if they belong to friends and family, and many food allergies are triggered because people do not realise they are eating food they are allergic to.

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 microscopic insects that breed in household dust. You can limit the amount of mites in your house by: 

• choosing wood or hard vinyl floor coverings instead of a carpet
• fitting roller blinds that can be easily wiped clean
• cleaning cushions, soft toys, curtains and upholstered furniture regularly, either by washing (at a high temperature) or vacuuming
• using tested allergen-proof covers on mattresses, duvets and pillow
• using a vacuum cleaner fitted with a HEPA (high efficiency particulate air) filter, because it can remove more dust than ordinary vacuum cleaners
• wiping surfaces with a damp, clean cloth, as dry dusting can spread the allergens further
• increasing ventilation and reduce humidity by opening windows and using extractor fans or dehumidifiers

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.

Pets

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

If you can't permanently remove a pet from the house, you should try: 

• keeping pets outside as much as possible, or limiting them to one room, preferably one without carpet
• not allowing pets in bedrooms
• washing pets at least once a fortnight
• regularly grooming dogs outside
• washing all bedding and soft furnishings on which a pet has lain (ideally at 60°C)

If you are visiting a friend or relative with a pet, ask them not to dust or vacuum on the day you are visiting, as this will stir up the allergens into the air. Taking an antihistamine medicine one hour before entering a pet-inhabited house can help to reduce symptoms.

Mould spores

Moulds can grow on any decaying matter, both inside and outside the house. The moulds themselves aren't allergens, but the spores they release are. Spores are released when there is a sudden rise in temperature in a moist environment, such as when central heating is turned on in a damp house, or wet clothes are dried next to a fireplace.

You can help prevent mould spores by:

• keeping your home dry and well-ventilated
• keeping internal doors closed when showering or cooking, to prevent damp air from spreading through the house, and using extractor fans
• not drying clothes indoors, store clothes in damp cupboards or packing clothes too tightly in wardrobes
• dealing with any damp and condensation in your home

When outdoors, you can help prevent contact with mould spores by avoiding:

• damp buildings
• buildings used to store hay or grain
• woods and rotten leaves, especially in damp conditions
• cut grass and compost heaps

Food allergies

By law, food manufacturers must clearly label any foods that contain something that is known to cause an allergic reaction. By carefully checking the label for the list of ingredients, you should be able to avoid an allergic reaction.

Many people 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 is a chance that different types of food could come into contact with each other, such as buffets or bakeries

Remember, simple dishes are less likely to contain "hidden" ingredients.

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

Pollen allergies

Pollen allergies – more commonly known as hay fever – are caused when plants (trees and grasses) release pollen particles into the air.

Different plants pollinate at different times of the year, so the months that you get hay fever will depend on what sort of pollen(s) you are allergic to. Typically, people are affected during spring (trees) and summer (grasses).

To avoid exposure to pollen you can:

• check weather reports for the pollen count and stay indoors when it is high
• avoid drying clothes and bedding outside when the pollen count is high
• wear wraparound sunglasses to protect your eyes from pollen
• keep doors and windows shut during mid-morning and early evening, when there is the most pollen in the air
• shower, wash your hair and change your clothes after being outside
• avoid grassy areas, such as parks and fields
• if you have a lawn, get someone else to cut the grass for you 

Read more detailed information on preventing hay fever.

Insect bites and stings

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

For example, when you are outdoors, particularly in summer, you can cover exposed skin, wear shoes and apply insect repellent.

Read more detailed information on preventing insect bites and stings.

Severe allergies

If you have ever had a severe allergic reaction (anaphylaxis), make sure you carry two adrenaline auto-injectors with you everywhere.

Wear a MedicAlert or Medi-Tag medallion or bracelet so that people are 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. Following this advice could save your life.