Allergens around you Dr Adrian Morris Allergens are common proteins in our environment that are harmless to most people but potentially life-threatening to those with allergies. They're present in our homes and gardens, whether we live in the city or countryside.

In this article

At home

Outdoor allergens

In hospital

The following are examples of allergens present in most homes throughout the year. They can cause constant irritation and inflammation of the nose, airways and skin.

• House dust mite droppings - these tiny, spider-like creatures are found all around the home, particularly in bedding (the average mattress contains about 10,000), carpets and soft furnishings
• Animal dander - tiny skin flakes covered in dried sweat and saliva, carried on the fur of cats, dogs, hamsters, guinea pigs, mice, rabbits and gerbils
• Bird feathers, cockroach droppings and mould or mildew spores
• Nuts, eggs, fish and milk in the diet
• Hair dyes, jewellery and leather goods

Don't smoke and discourage others from smoking in your home. Tobacco smoke isn't an allergen but it aggravates asthma and nasal allergies.

Silver birch pollen is the most profuse tree pollen allergen, followed by ash, London plane and oak

During spring and early summer - from March to May - tree pollens are the main outdoor allergen. Silver birch pollen is the most profuse tree pollen allergen, followed by ash, London plane and oak.

Grass pollens predominate from May to August, causing summer hay fever. Timothy and rye grasses produce large amounts of pollen, especially during hot sunny days following rainfall.

Oil seed rape pollen, although commonly implicated, isn't usually a cause of allergies. It's the volatile organic compound (VOC) chemicals released by rape flowers that cause nose and eye irritation during the summer.

In late summer, common weed pollens such as nettle, ragweed and dock may cause allergic symptoms.

Outdoor mould, such as cladosporium spores, grow on fallen leaves in autumn and can trigger seasonal outbreaks of asthma.

Horse hair is a potent allergen, and exposure at stables or on riding equipment may trigger asthma, rhinitis and even urticaria.

Latex rubber, found in surgical gloves, catheters, syringes and many medical appliances, can provoke allergies while in hospital or undergoing surgery.

Fluids given by intravenous drip, x-ray dyes, iodine used to sterilise skin and animal proteins in vaccines can all potentially cause allergies.

Medications are a common cause of allergies in hospital, especially penicillin, aspirin and anaesthetics.

This article was last medically reviewed by Dr Adrian Morris in September 2007.
First published in September 1999.